Circular Adders

On some adders, numbers were represented along an arc of a circle. People used their fingers or a stylus to enter numbers. On a few of these instruments, a mechanism allowed one to carry a single digit. These objects are described here as adders with carry. They blur the line between adders and adding machines.

This patent model for an adder with a single digit mechanical carry has a wooden base and a circular metal mechanism. At the center is a brass disc that has 100 holes around the outside.
Description
This patent model for an adder with a single digit mechanical carry has a wooden base and a circular metal mechanism. At the center is a brass disc that has 100 holes around the outside. Around it is a slightly elevated stationary ring, with the numbers from 1 to 9 engraved around it, representing 10, 20, etc, through 90. Between each of these numbers, smaller digits from 1 up to 9 are engraved. There is a stop at 0.
We know little about William M. Haines. The 1850 US Census for Rochester, New York, lists “William Hayes,” 38 years old, born in New York, who was a clerk living with W. V. K. Lansing, bookkeeper, and his family. The city directories for Rochester mention in 1845 a civil engineer named William Haines, living at 5 Elizabeth. He does not appear in the 1847 or 1849 city directories. In 1851, William Haines is listed as a clerk, with his home on 86 S. St. Paul. From 1853 through 1859, there was a dentist, William M. Haines, with an office at 32 Smith’s Arcade. He is not listed in the city directory for 1861, 1863 or 1864, but reappears in 1866 and 1867. He is not found in censuses of the period, nor in later city directories.
References: Scientific American, vol. 4, August 25, 1849, p. 388, account of machine.
William M. Haines. “Calculating Machine,” U.S. Patent #6403, 1849.
Location
Currently not on view
date made
1849
patentee
Haines, William M.
maker
Haines, William M.
ID Number
MA.252681
catalog number
252681
accession number
49064
This patent model for an adder with mechanical carry has a wooden handle and circular base on which three concentric brass discs and a brass arm are mounted.
Description
This patent model for an adder with mechanical carry has a wooden handle and circular base on which three concentric brass discs and a brass arm are mounted. The largest disc is glued to the base, and has the numbers from 1 to 99 indicated around the edge (there also is a blank space for zero). The middle and upper discs rotate about a central pivot, which has a smaller pin attached to it that holds the discs together. The middle disc is divided into 100 parts around the edge, with the parts numbered from 100 to 9,900 (again there is a blank division). The top disc has the numbers from 1 to 99 around the edge, as well as a blank. Next to each digit of the disc there is a small sunken tooth in the disc. A hole in the arm allows one to see numbers on the discs.
To use the instrument, one sets up thousands by rotating the middle disc. To add 1- or 2-digit numbers, one moves the arm counterclockwise so that it is over the desired number on the outer rim. Then, rotating clockwise back to zero, a spring-ratchet attached to the arm engages a tooth on the inner disc and rotates it through the number set up. (The spring-ratchet is missing from the model). According to the patent description, when the inner disc goes a full revolution, a carry mechanism advances the middle wheel one unit.
See U.S. Patent No. 11,726, issued September 26, 1854. There is an example of the instrument in the Home and Community Life collections. It's catalog number is 1978.0939.07.
”Aron” L. Hatfield (about 1818-1898) is listed in the 1850 US Census as living in Lewisburg, Union County, Pennsylvania. Born in Pennsylvania, he was 31 years old, had a wife and two children, and worked as a watchmaker. The 1860 Census lists an Aaron L. Hatfield, 40 years old, born in Pennsylvania and living in Green Springs, Sandusky, Ohio. He worked as an ambrotypist. No family is listed. The 1880 Census lists an Aaron L. Hatfield, 61 years old, widowed, and a watchmaker, who was living in Constantine, St. Joseph County, Michigan.
In addition to the patent for which this object is the model, Aaron L. Hatfield took out three other U.S. patents. The first, #103,327, was for an improvement in pruning shears, and was taken out May 24, 1870, when he was living in Clyde, Ohio. The second, #143,759, was for an improvement in pumps, and was taken out October 21, 1873, when he was still in Clyde. The third, #199705, was for an improvement in bag holders, and was taken out when he was living in Constantine.
According to an obituary in The Jeweler’s Circular and Horological Review, Hatfield died December 9, 1898, in Three Rivers, Michigan, where he was working as a jeweler and music dealer. By then he was living a secluded life above his store.
Reference: In addition to U.S. Census and U.S. Patent Office records, see “Death of Aaron L. Hatfield," The Jewelers Circular and Horological Review, vol. 37, December 14, 1898, p. 15.
Location
Currently not on view
date made
1854
patentee
Hatfield, Aaron L.
maker
Hatfield, Aaron L.
ID Number
MA.252684
catalog number
252684
accession number
49064
This patent model for an adder has a brass box with a rotating disc inset in the top. There are one hundred small holes around the rim of the disc. Outside the disc, on the top of the box, is a circular ring numbered from 01 to 99, with a gap at 00.
Description
This patent model for an adder has a brass box with a rotating disc inset in the top. There are one hundred small holes around the rim of the disc. Outside the disc, on the top of the box, is a circular ring numbered from 01 to 99, with a gap at 00. Outside of this are three rings of holes, with one hundred holes in each ring. These holes are to be used to hold markers indicating digits carried when the disc makes full rotations. On the side of the box is a rotating multiplication table.
A. Mendenhall, who patented this adder, was undoubtedly Amos Mendenhall, who was born in Ohio in 1828 and raised in east central Indiana. His father, Hiram Mendenhall (1801-1852) was a miller and farmer by trade and a Quaker and abolitionist in belief. In 1844, Hiram Mendenhall, as a representative of the Randolph County Anti-Slavery Society, presented a petition to presidential candidate Henry Clay, urging him to free his slaves. Clay refused and publicly rebuked Mendenhall. Hiram Mendenhall went on to pool his property with others to form the Unionport commune of the Society for Universal Inquiry and Reform. This effort soon collapsed and Hiram and Amos went to California to recoup the family fortunes in the gold fields. They failed to do this, and Hiram died of cholera on shipboard en route home. Amos, his mother, and his siblings continued to live in Unionport, where Amos farmed and tinkered. In the 1880 census, his occupation is given as “manufacture.”
The “practical calculator” was Mendenhall's first patented invention. He took out patents for gold mining devices (#360713, granted April 5, 1887, and # 541912, granted June 11, 1895), a tricycle (#453151, granted May 26, 1891), and a bicycle (#740156, granted September 29, 1903).
References: Patent #67,786, August 13, 1867 (Munn Co., attorneys); Scientific American, vol. 17, August 31, 1867, p. 141.
U.S. Census records for 1860, 1880, 1900.
Thomas D. Hamm, God’s Government Begun: The Society for Universal Inquiry and Reform, 1842-1846, Bloomington: Indiana University Press, 1996.
Location
Currently not on view
date made
1867
patentee
Mendenhall, A.
maker
Mendenhall, A.
ID Number
MA.252691
accession number
49064
catalog number
252691
This patent model for an adder has three concentric, linked discs that revolve on a central pivot. The bottom disc is numbered from 1 to 99 clockwise around its toothed edge, to represent hundreds and thousands.
Description
This patent model for an adder has three concentric, linked discs that revolve on a central pivot. The bottom disc is numbered from 1 to 99 clockwise around its toothed edge, to represent hundreds and thousands. Above it is a smaller disc, also with teeth around the edge, numbered from 00 to 99 clockwise to represent units and tens. A window in the third, top, largest disc shows the result on the dials below. The largest disc is numbered from 1 to 100 around the edge. Atop this disc is a rotating arm. Moving the arm counterclockwise advances the inner disc proportionally, allowing one to enter numbers up to 99.
A lever extends from the side of the disc and bends over the top. If the arm rotates around a full 100 units, it pushes this lever, causing a carry. The lever also may be used to zero the hundreds and thousands digits. See U.S. patent 69,647 for “Improvement in Tallying Instrument.” According to the patent, the invention “relates to a new and improved method of registering or tallying the quantity of lumber measured, or keeping account of sums of money paid out or received . . .”
There was a George Farmer (born about 1831 in England, died 1880 in Saginaw, Michigan) who worked as a miller and shingle maker in Illinois and in Michigan. He is listed in the 1860 U.S. Census as living in Elmira in Stark County, Illinois, working as a miller. That same year he received a patent on August 21for an improvement in harvesters (#29685). By 1870, he was living in Saginaw, Michigan, still working as a miller. In the 1880 Census he is listed as a shingle manufacturer. He and his son, Albion, ran a shingle-making business in Saginaw under the name of George Farmer & Son. It is listed in the 1878 city directory for the town. The George Farmer who received the patent for this adder was a resident of Flint, which is near Saginaw.
Reference: George Farmer, “Improvement in Tallying Instrument,” U.S. Patent 69,647, granted October 8, 1867.
Location
Currently not on view
date made
1867
patentee
Farmer, George
maker
Farmer, George
ID Number
MA.252692
accession number
49064
catalog number
252692
This instrument consists of two concentric brass discs, one rotating inside the other. The rim of the outer disc has the numbers from 0 to 99 engraved around its edge. The inner disc has 100 small holes marked evenly around its edge. These also are numbered 0 to 99.
Description
This instrument consists of two concentric brass discs, one rotating inside the other. The rim of the outer disc has the numbers from 0 to 99 engraved around its edge. The inner disc has 100 small holes marked evenly around its edge. These also are numbered 0 to 99. Two steel arms pivot at the center of the inner disc. The longer arm has a pin on the underside that fits into the holes and a small knob on the upper side so that it can be rotated. A protruding pin set at 0 in the outer circle stops the motion of this arm. It is used to add numbers up to 99.
When the total on the inner disc exceeds 99, the smaller arm advances one digit, indicating hundreds. Hundreds apparently cannot be entered directly. The adder is painted black on the reverse side and has a support attached to the back so that it sits at an angle. A green paper label glued to the back gives directions for use.
Census records list two men, one of whom may have been Alonzo Johnson, the co-inventor of this device. Both were machinists. Alonzo Johnson (no middle initial) was born 12 February 1828 in Bangor, Maine, the son of Louisa Underwood and Dolliver Johnson. Dolliver Johnson, a railroad engineer, became a superintendent of locomotive power on the Fitchburg Railroad in Massachusetts and then was associated with the Illinois Central in Illinois. His son Alonzo Johnson married in about 1850, and lived in Springfield, Massachusetts, with his wife, Sarah, and their children from at least 1870 through 1900. Census records also list Alonzo H. Johnson, born about 1828 in Connecticut, who was living with his wife, Hannah, also in Springfield, in 1870, 1880 and 1900.
One of these Alonzo Johnsons took out eight patents. The first two were for calculating devices. These were #73732 (granted January 28, 1868, with James A. Loomis as co-inventor and Charles Gifford of Gardiner, Maine, as assignee), #85229 (taken out December 22,1868 and assigned to Sylvester Bissell and Andrew West of Hartford). Later patents were for nut-locks (#188055, granted March 6, 1871), slitting lock nuts (#231492, granted August 24, 1880), a car-brake (#235152, granted December 7, 1880), a card-cutter (#241372, granted May 10, 1881), a sash-fastener (#255144 - granted April 11, 1882), and a gumming device for envelope machines (#397798, granted February 12, 1889).
James A. Loomis, the co-inventor of this device, is probably the James Loomis listed in United States Census records for 1860, 1870, and 1880 as a resident of Springfield, Massachusetts. He is listed in 1860 as a 45-year-old wheelright, in 1870 as a 57-year-old carriage maker born in Massachusetts, and in 1880 as a 67-year-old retired carriage maker.
The “Conkey” referred to in the name of the device may be Henry Conkey, who is listed as a 27-year-old machinist in Enfield, Massachusetts, in the 1860 Census and as a 35-year-old machinist in Springfield, Massachusetts, in the 1870 U.S. Census.
References: James A. Loomis and Alonzo Johnson, “Improvement in Calculating Machines,” U.S. Patent 73732, 1868.
P. Kidwell, “Adders Made and Used in the United States," Rittenhouse, 1994, 8:78-96.
Location
Currently not on view
date made
1868
maker
Conkey & Loomis
ID Number
1990.0318.01
accession number
1990.0318
catalog number
1990.0318.01
This patent model for an adder has as its base two concentric brass discs, one rotating inside the other. The rim of the outer disc has the numbers from 0 to 99 engraved around its edge. The inner disc has one hundred small holes marked evenly around its edge.
Description
This patent model for an adder has as its base two concentric brass discs, one rotating inside the other. The rim of the outer disc has the numbers from 0 to 99 engraved around its edge. The inner disc has one hundred small holes marked evenly around its edge. These also are numbered 0 to 99. Two steel arms pivot at the center of the disc. The longer arm has a pin on the underside that fits into the holes and a small knob on the upper side so that it can be rotated. A protruding pin set at 0 in the outer circle stops the motion of this arm. It is used to add numbers up to 99.
When the total on the inner disc exceeds 99, the the smaller arm advances one digit, indicating hundreds. The number of hundreds entered appears in a window in a small disc that is on top of three relatively small gears concentric to the large discs. Hundreds apparently cannot be entered directly. The adder has a handle that projects from the center of the back.
Census records list two men who may have been Alonzo Johnson, the inventor of this device. Both were machinists. One Alonzo Johnson (no middle initial) was born 12 February 1828 in Bangor, Maine, the son of Louisa Underwood and Dolliver Johnson. Alonzo's father was a railroad engineer, then a superintendent of locomotive power on the Fitchburg Railroad and then associated with the Illinois Central. This Alonzo Johnson married in about 1850, and lived in Springfield with his wife Sarah and their children from at least 1870 through 1900. Census records also list an Alonzo H. Johnson, born about 1828 in Connecticut, who was living with his wife Hannah in Springfield in 1870, 1880 and 1900.
Alonzo Johnson of Springfield took out eight patents, the first two for calculating devices. These were #73732 (granted January 28, 1868, with James A. Loomis as co-inventor and Charles Gifford of Gardiner, Maine, as assignee), and #85229 (taken out December 22,1868, and assigned to Sylvester Bissell and Andrew West of Hartford). Later patents were for nut-locks (#188055, granted March 6, 1871), slitting lock nuts (#231492, granted August 24, 1880), a car-brake (#235152, granted December 7, 1880), a card-cutter (#241372, granted May 10, 1881), a sash-fastener (#255144, granted April 11, 1882), and a gumming device for envelope machines (#397798, granted February 12, 1889).
Compare to 1990.0318.01.
Reference: Alonzo Johnson, “Improvement in Calculating-Apparatus,” U.S. Patent 85,229, December 22, 1868.
P. Kidwell, "Adders Made and Used in the United States," Rittenhouse, 1994, 8:78-96.
Location
Currently not on view
date made
1868
patentee
Johnson, Alonzo
maker
Johnson, Alonzo
ID Number
MA.252695
accession number
49064
catalog number
252695
This patent model for a circular adder has a wooden base that supports three concentric wooden rings and a central mechanism. The outer fixed ring is serrated around the outer edge.
Description
This patent model for a circular adder has a wooden base that supports three concentric wooden rings and a central mechanism. The outer fixed ring is serrated around the outer edge. The 100 serrations are numbered in ink from 1 to 99 (the 0 serration isn’t numbered) on a paper ring glued to the surface of the ring. Inside this ring is a movable ring, with 100 upward-facing serrations around its edge. These are numbered on an adjacent piece of paper from 00 to 99. Inside this ring is a third fixed ring, serrated on the inside, and also carrying a numbered slip of paper numbered from 00 to 99.
Two wooden arms are mounted on a rotating wooden platform at the center of the instrument. The larger arm is designed to link to the two outer rings and the smaller one to the middle ring only. The machine has a carry from the tens to the hundreds place. It is intended to be used for adding columns of figures, two places at a time. The machine was patented by Elmore W. Taylor of Franklin, Indiana, in 1874.
Earlier, Elmore W. Taylor of Franklin, Indiana, took out patent 56464 for an evaporator (relating to furnaces) on July 17, 1866. Elmore W. Taylor of Detroit, Michigan, took out a patent for a card and picture holder in 1883 (#274052). Elmore W. Taylor of Johnson County, Indiana, married Maggie A. Toner on October 5, 1876. The 1880 US Census lists an “Elmer W. Taylor,” photographer, age 31, born in Michigan with parents born in New York, who was living in Detroit with Margaret A. Taylor, age 21, who was born in Indiana. Hence it seems likely that all three patents were held by the same inventor.
Reference: U.S. Patent 155772, October 6, 1874.
Location
Currently not on view
date made
1874
patentee
Taylor, Elmore W.
maker
Taylor, Elmore W.
ID Number
MA.309325
accession number
89797
catalog number
309325
This round metal patent model for an adder with carry has a cylindrical case that contains two concentric rotating rings, each with the digits from 0 to 99 engraved evenly around the edge.
Description
This round metal patent model for an adder with carry has a cylindrical case that contains two concentric rotating rings, each with the digits from 0 to 99 engraved evenly around the edge. The outer, lower ring, with digits representing hundreds, is slightly larger than the other ring. Atop these is a metal disc with two adjacent windows, which make it possible to see the digits on the discs below. On top of this disc is a flat ring with four spokes that hold it together. This ring is the size of the lower ring. This ring also has 100 divisions around the outside, which are engraved with numbers. There is a window at 1 that allows one to see the disc below. This spoke has a small knob for rotating it.
Rotating this ring so that a number on it is opposite a stop projecting over the ring adds the number to the total already indicated. When the inner ring advances past 99, there is a carry to the outer ring. There is also a knob on the bottom of the machine for advancing or zeroing the hundreds ring, as well as a strap for carrying it.
According to the 1870 US Census, Calvin J. Holman, age 39 (hence born about 1831) was a Massachusetts native who was living in Sylvania Township, Lucas County, Ohio. He was the proprietor of a mill, and had substantial holdings in real estate. Also in the household were his wife, Adelia, (age 35) and children Della (16), Delvin (14), and James (11). Holman is also listed in the 1880 Census as living in Toledo and working in “spring manufacture.” Living with him were Adelia, a daughter Emma S., 23 years old and born in Pennsylvania, a son Delvin J. (21), born in Wisconsin, and a son James H. (20), also born in Wisconsin.
In addition to this adding machine, Holman patented several inventions closely related to milling. These included an improved sawing machine (U.S. patent 40837, granted December 8, 1863) and a machine for sawing staves (U.S. Patent 51,896, granted January 2, 1866), both to Calvin J. Holman of Oshkosh, Winnebago County, Wisconsin. Calvin J. Holman of Chicago was granted U.S. Patent 72639 (December 24, 1867) for a machine for sawing barrel heads. On May 29, 1877 he was granted a patent (#191428) for an improvement in vehicle springs, which may have led to his work in spring manufacture. There are several later patents granted to Calvin J. Holman or Calvin James Holman of Chicago, which also may be associated with this inventor. No record of him was found in either the 1860 or the 1900 U.S. Census.
Reference: U.S. Patent 153826, August 4, 1874.
Location
Currently not on view
date made
1874
patentee
Holman, Calvin J.
maker
Holman, Calvin J.
ID Number
MA.309331
accession number
89797
catalog number
309331
The instrument consists of three concentric brass discs, a brass marker, a steel stop, and a wooden handle (instrument must be removed from box to find handle). Each brass disc has the numbers from 0 to 99 stamped around the edge.
Description
The instrument consists of three concentric brass discs, a brass marker, a steel stop, and a wooden handle (instrument must be removed from box to find handle). Each brass disc has the numbers from 0 to 99 stamped around the edge. The two inner discs both have a circle of 100 holes just outside the numbers. The inner holes are used to add the last two digits of a number by rotation. Any hundreds value in the sum carries to the second set of holes, which are used to add hundreds and thousands places.
The machine is in a cylindrical wooden case with cover.
According to the Kirksville [Missouri] Democrat for August 2, 1888, by then Hart had sold 3500 of these devices and “he lately ordered one thousand more.”
References: U.S. Patent #199289
P. Kidwell, "Adders Made and Used in the United States," Rittenhouse, 1994, 8:78-96.
Kirksville [Missouri] Democrat, August 2, 1888.
Location
Currently not on view
date made
1878
patentee
Hart, William
maker
Scovill Manufacturing Company
ID Number
1993.0510.01
accession number
1993.0510
catalog number
1993.0510.01
This U.S. Patent Office model for an adder has a square wooden frame. On top is a piece of paper printed with the numbers from 1 to 100 and a rotating tin disc.
Description
This U.S. Patent Office model for an adder has a square wooden frame. On top is a piece of paper printed with the numbers from 1 to 100 and a rotating tin disc. The disc has 100 holes in it and is covered with another piece of paper, with the digits from 1 to 100 printed around the edge. Atop this disc is a second, smaller wooden disc with ten serrations around the edge. There also is a fixed metal arm which reaches over the 100 disc on the outside paper. This arm advances the smaller disc at every rotation of the larger disc.
Census records suggest that the inventor of this device was born in Connecticut or Massachusetts in about 1813. The 1840 U.S. Census indicates that there was a William M. Briggs, 20 to 30 years old, living with a woman of about the same age and two children in Stoughton, Norfolk County, Massachusetts. No record for William Briggs was found in the 1850 census for Massachusetts. The 1860 Census returns list a William Briggs, 47 years old and a farmer, living with Elizabeth, 32 years old, and children Emma (10), Frank (5), and George (2). This William Briggs was supposedly born in Massachusetts. The family lived in Sharon, Norfolk County, Massachusetts, a town very close to Stoughton, Massachusetts. In the 1870 Census for Stoughton, Norfolk County, Massachusetts, there was a William M. Briggs, miller, 57 years old, born in Connecticut. He reportedly lived with Elizabeth (age 43) and a five-year old boy.
References: U.S. Patent 222,126, December 2, 1879.
P. Kidwell, “Adders Made and Used in the United States,” Rittenhouse, 1994, 8:78-96.
Location
Currently not on view
date made
1879
patentee
Briggs, William M.
maker
Briggs, William M.
ID Number
MA.311959
accession number
155183
catalog number
311959
This U.S. Patent Office model for an adder has a wooden frame with a round brass top and mechanism. A toothed disc under the top has the digits from 0 to 99 indicated on it in ink. The 99 complement also is indicated, for use in subtraction.
Description
This U.S. Patent Office model for an adder has a wooden frame with a round brass top and mechanism. A toothed disc under the top has the digits from 0 to 99 indicated on it in ink. The 99 complement also is indicated, for use in subtraction. To the right of the disc is a series of pins labeled from 1 to 10. An arm extending from the right side of the disc fits between the pins. Pulling the arm forward advances the disc by the amount indicated on the scale. When the disc has advanced a full rotation, it advances a smaller, vertically mounted disc on the left side by one unit. Complementary units are also indicated on the edge of this disc. The device also has a set of nine wooden digit wheels, with paper around the edge, at the front. These are intended for keeping track of numbers used in calculations.
According to the 1900 U.S. Census, Christian W. Hergenroeder was then 36 years old and living in Baltimore. He was born in Germany of German parents, immigrated to the United States in 1882, and was a naturalized citizen. His wife, Sofia, was born August of 1866, also in Germany of German parents, and came to the United States in 1891. She apparently was not naturalized. Their son, Christian Jr., was born November of 1895. Both parents could read, write, and speak English. Christian's occupation was given as laborer. The family lived in a rented house. Hergenroeder was not found in 1880, 1910, 1920 or 1930 U.S. Census records.
Another patent was granted to Christian W. Hergenroeder of Baltimore, for an improvement in music leaf turners. He applied for this patent on January 5, 1882, and was granted it on October 10, 1882 (#265602).
Reference: U.S. Patent No. 263904, September 5, 1882.
Location
Currently not on view
date made
1882
patentee
Hergenroeder, Christian W.
maker
Hergenroeder, Christian W.
ID Number
MA.311960
accession number
155183
catalog number
311960
This aluminum device consists of two discs sealed together at the rim, with a rotating disc in between. Various numbers are stamped around the rim of the rotating disc. Openings in the outer discs reveal three numbers on either side at one time.
Description
This aluminum device consists of two discs sealed together at the rim, with a rotating disc in between. Various numbers are stamped around the rim of the rotating disc. Openings in the outer discs reveal three numbers on either side at one time. One side of the instrument has the numbers from 1 to 20 stamped clockwise around the scalloped rim of the movable disc. The other side of this disc has the numbers from 21 to 40, also stamped clockwise.
At the top of the instrument, three alternate numbers are visible (i.e., 1, 3, 5). Three alternate numbers also are visible on the reverse side (i.e., 35, 37, 39). The sum of two numbers on opposite sides of the disc is always 40 (i.e., 1 and 39). Part of the scalloped edge of the movable disc is exposed at the bottom.
Clay W. Prewett and the Prewett Addograf and System Company (also known as the Prewett System Company) of Los Angeles, California, sold this device. A 1940 brochure describing “The Prewett Addograf and System” indicated that it consisted of not only this instrument but a $10 brochure describing how it worked, a $5 brochure on modern short cuts in multiplication, division, interest, fractions, and mixed numbers; and a $5 multiplication chart. The entire system could be purchased for $15. It was not returnable.
Location
Currently not on view
date made
1940
maker
Prewett System Company
ID Number
MA.155183.28
catalog number
155183.28
accession number
155183

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