Hamilton 992E

Hamilton Grade No. 992E, 16-size, 21-jewel, adjusted to isochronism, temperature and 5 positions, lever-set, with an Elinvar hairspring and Montgomery Dial - mfg circa 1936. The name Elinvar was derived from the term "Elasticity Invariable" and was the first alloy to resist the changes in elasticity that occur with changes in temperature helping ensure even more consistent accuracy.