This is an original WWII U.S. Marine Corps camouflage helmet cover. This variation, with the the buttonhole slits in the body as well as the flaps, is often referred to by collectors as a 'third pattern' cover, but in actuality was the first type, produced in 1942. This particular one is in superb condition; cut-outs for the chinstraps to pass through haven't even been created, meaning this cover most likely hasn't sat on a helmet before. There are no E.G.A.s on either side of the cover.
Early-WWII U.S.M.C. Camouflage Helmet Cover (Mint)