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Keuffel and Esser Model 68-1251 Log Log Duplex Decitrig

• Type: Log Log Duplex
• Size: 10 Inches / 25 cm
• Material: Plastic, aluminum brackets
• Scales:
  • Front: LL02 LL03 DF [ CF CIF CI C ] D LL3 LL2
  • Back: LL01 L K A [ B T SRT S ] D DI LL1
• Serial Number: 120206
• Date of Manufacture: Early 1963
• HvH: 4251

By the mid 1950's, plastics had come to the point where one could manufacture a reliable instrument from a stable polyethylene or polyvinyl, and Keuffel and Esser started making slide rules therefrom. This substance K+E called "Ivorite". I don't think it feels much like ivory, myself. Your milage may vary. Unlike the latest generation of plastic rules, these had an adjustable top stator, suggesting that their confidence in the new material was, if high, not complete.

This is a remake of the venerable N4081-3 log log decitrig rule.

The serial number, 120206, suggests a manufacture date in early 1963.