The movement serial number is G355819. Hamilton G-prefixed serial numbers track their premium rectangular wrist movements. Based on historical manufacturing records, this serial number dates the production of the movement to approximately 1941.

It is an American-made, 17-jewel manual-wind mechanism. The "F-S" indicator near the balance wheel stands for Fast/Slow, which a watchmaker uses to adjust the timing.

The Grade 980 was one of Hamilton's workhorse calibers utilized in their highly collectible Art Deco and pre-WWII rectangular dress watches.