Slide rule with case; a. White plastic slide rule with logarithms; 31.0 x 4.5 cm. approx. b. Small half of blue plastic case with strap, 13.5 cm x 6.5 cm. approx. c. Larger half of case with inner plastic extension; 26.5 cm x 6.5 cm approx. Used in Trigonometry for measuring logarithms. Made in U.S.A. by Sterling,, #594, copyright 1965.