Size 7.75. Classic WW2 signet style, lightweight brushed aluminum, very well made (but still handmade and finished) by a serviceman with access to tools like a polishing wheel, maybe in a machine shop or naval vessel repair shop. Unengraved 3/4" x 5/8" head with clipped corners. Brutalist/minimalist. Anticipates modernist jewelry. Industrial design-y! Was this meant to be a sample, like later engraved to a serviceman's specifications?