Aeronautical engineer George Norman Albree (1888–1986) designed airplane components and slide rules. This is an example of his Duplex slide rule, which he intended to be used by grade school children. It is printed on both sides of a cardboard circle and consists of a logarithmic spiral scale for numbers from 10,000 to 32,100 on the front or "A" side and numbers from 31,170 to 100,000 on the back or "B" side. A rotating clear plastic indicator wraps around both sides.
On both sides, the center of the spiral is marked: ALBREE TRULOG DUPLEX (/) MODEL 18. Inside the fifth ring of the spiral on the front, the instrument is marked: ©1945 (/) G. NORMAN ALBREE (/) BOSTON MASS. The instrument arrived with a plain square paper case, an instruction manual, and a green paper bag. The cover of the manual reads: MANUAL (/) of the (/) TRULOG DUPLEX (/) Precision Pocket Calculator (/) Multiply - Divide - Raise to Any Power - Extract Any Root. The booklet was copyrighted in 1948. The bag is marked: THE (/) TRULOG DUPLEX (/) With Right Hand Instruction System.
Albree renewed the copyrights for the Albree Trulog Duplex (R560370) and Albree Trulog Spiral (R560371) in 1973. See also MA.335486 and MA.335487.
References: Timothy Hughes, "The George Norman Albree Papers," New England Ancestors 5, no. 3 (2004): 46, http://www.americanancestors.org/PageDetail.aspx?recordId=134553447; Library of Congress, Catalog of Copyright Entries, Part 4, n.s. 40 (1945 index): 287; Catalog of Copyright Entries: Books: Part 1A, 3rd ser. 2, no. 1 (1948): 313; Library of Congress Copyright Office, Renewal Registrations: Works of Art (July-December 1973): 476; Henry W. Syer and Donovan A. Johnson, "Aids to Teaching," Mathematics Teacher 43, no. 5 (1950): 215–221, on 220; accession file.
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