A group of eighteen circular slide rules and calculators, comprising: Scientific Instruments circular clide rule, No. 300-b with box and case, a Cruver computer, altitude correction AN5837-1 with box, a 1945 Aircraft Instrument true airspeen computer type G-1, by Crowe, with original mailing package, a GCT computer model number Mil-C-4597A by G. Felsenthal and Sons, a Grumbacher paper color computer, a Pickett Circular slide rule model 110ES with case, (2) Scientific Instruments circular slide rules (1961) model no. 300B with cases, a Lietz Stadia Computer No. 3526-25 with case, a Weems & Plath Marine Navigation Star Finder 2102-D, a Concise Stadia Computer, a booklet, "The Carpenter's Slide Rule". third edition published by John Rabone and Sons, a circa 1940 Binary Slide Rule, a date finder Guco 1004, a paper USPS calculator, (2) Staedtler model 5621 PSI proportional scales, a Computer, Air Navigation Celestial Azimuth type CP-300/U by Allegheny Plastics, a PS 80 Proportional Scale, by C-Thur Ruler Company, an unmarked 1934 example, a Cox's Stadia Computer and a 1936 example (unknown maker and model), Largest diameter 8 1/4in Each in generally good condition overall. Typical scuffs, scratches and bending.