A 20th Century American centre seconds lever by Hamilton in a silver open face case. High quality 22 jewel 4992B model, damascened nickelled split three quarter plate keyless movement with going barrel. Plain cock with polished steel micrometer regulator. Uncut balance with overcoil Elinvar-Exra hairspring. Club foot lever escapement, escape and lever pivots with endstones. Signed white dial with centre seconds, bold black Arabic numerals and smaller chapter within for the hours 13 to 24, blue steel hands. Plain silver open face case with screw back and bezel, marked “Keystone – Silver – 800 Fine”.