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Keuffel and Esser Model N4081-3 Log Log Duplex Decitrig

• Type: Log Log Duplex
• Size: 10 Inches / 25 cm
• Material: Mahogany and celluloid
• Scales:
  • Front: LL02 LL03 DF [ CF CIF CI C ] D LL3 LL2
  • Back: LL01 K A [ B T ST S ] D L LL1
• HvH: 4243

The 4081-3 first came out in 1937, as a variant to the 4080-3. Where the 4080-3 divided a degree of arc into minutes, the 4081 divided the degree into tenths, thus "decitrig". This symbolized, finally, the slide rule's move from math and physics into engineering.

This is from the second generation of K&E's log log trig rules, starting in the 1940's. Rule identification data has moved to the top edge of the rule.

The serial number, 674914, suggests a manufacture date in about 1950.