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Posted by / 20-Jan-2018 01:28

Another beautiful K&E rule, bearing hyperboic sine (Sh1, Sh2) and tangent (Th) scales for electrical engineers.

What's odd about this rule is that it has short codes on the ends of the parts, as well as serial number The serial number on this N4041, 112404, dates it to around 1925.He first imagined a portable mechanical calculator in the late 1930s, but the invasion of the German army put these aspirations on hold, particularly once he was hurled into a concentration camp.But the Nazi's were privy to his technical savvy, and offered him a reprieve by way of a position in a slave-labor factory building precision parts for secret military projects.Herzstark and his fellow prisoners would be freed in 1945, by which point the engineer had drawn up detailed designs.He took these to a German factory where machinists were able to produce three working prototypes of what is considered to be the first mechanical calculator small enough to fit in a pocket.

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The label on the rear was vastly changed in 1927-28.