“Dietrich Gruen” Gruen Watch Co. , Cincinnati, Ohio and Bienne, Switzerland, “Dietrich Gruen”, No. 42468, case No. 104232. Made circa 1920. Very fine and rare, keyless, 14K pink gold dress chronometer with 32-hour power reserve indicator. Four-body, "demi-bassine", polished, gold hinged cuvette. Champagne with stylized painted Arabic numerals, outer minute track, sector for the up-and-down indication, recessed subsidiary seconds dial. Blued steel "cathedral" hands. Cal. 250, rhodium-plated, 23 jewels, some in screwed gold chatons, straight line lever escapement, cut bimetallic "chronometer" compensation balance adjusted to temperatures, all positions and isochronism, blued steel Breguet balance spring, “swan-neck” micrometer regulator, “wolf’s-tooth” winding wheels. Dial and movement signed, case numbered. Diam. 47 mm. Notes A Gruen watch with power-reserve indication is very rare; only a very few were produced.