5.7 Felsenthal, USA

A skilled jeweler and watchmaker in Louisville, Kentucky, Gabriel (“Gabe”) Felsenthal (1856-1925) moved to Chicago in 1892 to join other family members in the big city. Here, he partnered with two cousins who formed the Felsenthal Bros. & Co., not far from the location of the company formed by his two brothers, Adolph and Lee – the Ad-Lee Novelty Co. – in downtown Chicago. In 1898 he ventured out on his own and formed G. Felsenthal & Co. which led Gabe eventually to become involved with the newly-formed motion picture industry. By the late 1910s, just before World War I, the company was re-incorporated into G. Felsenthal & Sons, with his children Lester and Irving joining Gabe in the enterprise. It was at this time that the company re-positioned itself to become a purveyor of advertising novelties such as cheap ink pens and small toy-like items, so-called “tchotchkes”, sold to local businesses.

Gabe died in 1925 and his sons were determined to maintain their dad’s vision of the company. The great depression and early World War II times made their business difficult, and when the U.S. entered World War II in the early 1940s, the manufacturing of trinkets was put on hold. In response, Felsenthal used their skills in plastics and mechanical toys to end up making roughly 80% of all the plastic aviation instruments used by the U.S. in the war effort. Several companies manufactured flight computers during the war, such as the Dalton Dead Reckoning Computer. But the bulk of these devices was made by Felsenthal, and the company quickly became well recognized in the aviation business for the quality of their computing equipment. 1944 Felsenthal ad

While Felsenthal made a variety of aviation computers, they appear to have made only one “standard” slide rule, the Felsenthal Logarithmic Calculator. But, while not labeled as such, each Dalton-style aviation computer has two circular scales which are the equivalent of C and D scales that can be used for standard multiplication and division problems.

The interested collector is encouraged to visit the article at the Made in Chicago Museum (from which the above information, including the advertisement, was obtained) for many more details of the Felsenthal legacy.

Total number of Felsenthal slide rules in the collection: 5. \(~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\)

Model Year Type Mat L0 Case Notes
AN 5837-1 1943 C pl 60 box Altitude Correction Computer; B/W main spiral scale, with fluorescent markings; WWII
D-4 1944 C pl 12 no Time Distance Computer Type D-4; WWII device; Property of U.S. Army Air Forces; fluorescent numbers on black background
FAA-95 1950-1955 C pl 16 no MB-1 Computer, Air Navigation, True Airspeed and Altitude; true altitude correction spiral on back
Logarithmic Calculator FF-6 1951 C pl 12 yes G. Felsenthal & Sons, Chicago; instructions and paper pouch
Dial-A-Con 1968 C pl 9 yes Flight computer, Type E6B, with instruction manual (by A. Fuchs), and vinyl case