This stepped drum, manually operated non-printing calculating machine has a brass and steel mechanism that fits snugly in a wooden case. Each of the seven levers for setting digits has a stepped drum below it. The brass plate that covers the drums is painted black. Slits in the plate allow the levers and other parts to move. The edges of the slits next to digit levers are numbered from 0 to 9 to indicate the number entered. An ADD. MULT. / SUB. DIV. lever is left of the digit levers. A compartment covered by a slate is left of this. The operating crank is right of the levers.
The carriage behind the levers has seven windows for the revolution counter register, and 12 windows for the result register. It can be placed at seven different positions. A mark on the cover plate assists in positioning the carriage. Holes for decimal markers are between the levers and between the holes of the registers, as well as sliding decimal markers for the result register. Thumbscrews allow one to set numbers in the registers. Zeroing levers for these registers on the right of the carriage may be operated jointly or individually. The case has two legs that may be used to set it at an angle, as well as a lock and key.
A mark to the left of the levers reads: BUNZEL (/) TRADE DELTON MARK. Left of this is the mark: FACTORY VIENNA. The serial number, on the edge of the case at the back, is 5310.
Hugo Bunzel, a calligraphy teacher and former painter in Prague, designed the machine, which was introduced in 1908 and produced through 1915. It was manufactured in Vienna. This example is from the collection of Felt & Tarrant Manufacturing Company.
E. Martin, The Calculating Machines (Die Rechenmaschinen), trans. P. A. Kidwell and M. R. Williams, Cambridge: MIT Press, 1992, pp. 198–199.