Keuffel and Esser 4092-3

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Keuffel and Esser Model 4092-3 Log Log Duplex

Type: Log Log Duplex
Size: 10 Inches / 25 cm
Material: Mahogany and celluloid
Scales:
- Front: K DF [ CF CIF CI C ] D L
- Back: LL0 A [ B S T C ] LL3 LL2 LL1
HvH: 4326

Obverse

Reverse

An early log log rule. This version, the 4092-3, was intruduced in 1922 and differs quite a bit from the previous 4092 rule, although intended for the same function. The catalog lists this as model N4092-3, but the 'N' notation is not marked on the rule. This rule last appeared in the 1937 catalog, which also introduced the 4080-3 and 4081-3 log log trig rules.

Three scales for positive exponents of e are typical. The LL0 scale for negative exponents of e is unusual. Typically a lone LL0 scale would give results for e^-0.1 to e^-1. This LL0 scale is two partial scales in one, and is read against the A/B scales. From A=1 to A=30, the scale returns e^-0.1 to e^-3. From A=30 to A=100, the scale returns e^-0.03 to e^-0.1. For some reason, the ends of this scale are marked 'e', even though these points have value e^-0.1.

The original owner penned his name, address, telephone number and college into the inside of the case flap. The leather is rough here and some of the data faded. One can read "Bernard Baumgartner, Reed College, ... E 78 N, ... 7863". This helps date the purchase of the rule. Reed College is in Portland, Oregon, and in late 1931 the City of Portland issued an edict (er, an ordinance) changing every house address in the city. E 78th N became NE 78th and the house number changed. Mr. Baumgartner graduated Reed College in 1935.

The serial number, scale selection, typeface and cursor style are consistent with rules made between 1930 and 1933.