WW2 US Navy so named "sailor flat hat", as the top part is flat with a metal ring inside. Regulatory in the US Navy since 1852, the “flat hat” coexisted for 20 years with the other rimless model ("Donald Duck Hat"), which finally prevailed, although during WW2 the "flat hat" was the most used model. On the inside, written in stencil characters, is the name of the ship to which the cap belonged: E.C. Ellis - later USS Ellis DD-154-, a wickes-class destroyer that served in the US Navy before and during WW2 with anti-submarine duties, escorting troops to Iceland and guarding transatlantic convoys between 1939 and 1945. "Ellis" is shown on the last photo (not included). Worn "US Navy" headband after 1941, when surrounding headbands with specific ship names were banned. Leather sweatband in good condition. US size 7 (EU equivalent size 55/56). Overall a good example of naval warfare during WW2.