Hyperbolic Match Output
Model:Duplex Slide Rule No. 255 (For Expert Electrical Engineer) Version 1
Scales Front: || L, K, DF || CF, CIF, CI, C || D, X , Θ || NOTE: X is radians and Θ is degrees.
Scales Back: ||Sh1, Sh2, Th, A || B, TI2, TI1, SI, C || D, LL3, LL2, LL1 ||
Gauge Marks: π is on CF and DF and π/2 is on X and SI; mark c is on back scale C.
Construction: 25cm.; Plastic face on laminated wood ; Cursor is framed. Adjustable metal brackets.
Date: 1951 - 1958
Source: Rod's Top Rules from eBay