This is a 1942 Trigonometry calculator with two, 2, sides that provide the Algorithms for three, 3, sided triangle.  I.E. D side cosign calculation gives algorithm top of C2+ A2 – B2 over 2 x C x A.  This treasure is stamped Trig Easy trade mark Makes Trigonometry Easy; Manufactured by E.H. Needham Culver City California; Copyright 1942 E. H. Needham.   It is made of cardboard with inside circular answers for A B C D or E Algorithms answers.  Size is 4 x 3 inches in good operational condition.  Collectors of antique calculators from 66+ years ago will find this a highlight to their collection.