Size 10. Made out of an aluminum machine part - threaded interior can still be seen - for wear by a serviceman. Classic WW2 signet style. Aluminum was a futuristic material in the 1940s, symbolically tied to aviation, modernity, and military technology, associated with speed. Almost talismanic and widely available. Lightweight, relatively soft, and easy to manipulate. The man who made this may have worked in or near a machine shop, with access to tools like alphabet punches - the initials (or word) PAL are naively stamped on top. An identifying piece, or a gift of friendship?