Hyperbolic Match Output
Maker:ECKEL (The Eckel Co., USA)
Model:Engineer's Log Log (Circular Slide Rule)
Scales Front: || LL1, LL2, LL3, LL4, C || D, DI, A, K, L || Scales are printed on cursor
Scales Back: || SH1, SK2, TH, D, ST, S, T < 45°, T > 45° || Scales are printed on cursor
Construction: Diameter about 8".
Information: This is the only known circular slide rule with hyperbolic scales that was manufactured and sold to the public. (See Appendix regarding, "The Everitt Complex Hyperbolic Slide Rule of 1924").