The Rem 511, part of the Remington 5-teen series (510, 511, 512, 513, & 521) was mfg'd from 1939-1962 with approx 375,000 made. Was mfg'd in both 511 A & 511 P configuration with the "P" having receiver mounted aperture (peep) sight. None were serial numbered until 1954 & probably not all after that?? I have a 1961 model with no SN. After around 1956 or so, some (but not all) were grooved for tip-off scope mount. In 1962 Remington began mfg of the 511-X model (along with 510-X & 512-X) & continued until 1968 (approx 29,120 511-X's mfg'd. The "X" models were virtually identical to the earlier models except for a different wood finish & improved sights. Date of mfg code is stamped on left side of barrel, right in front of the receiver, just above wood line. It consists of two or sometimes three letters, AC, XUU, BSS, etc, often preceeded or followed by a symbol of some kind, star, anchor, #, etc. The stamped symbols are merely inspector/proof marks & are not related to the date code. Code meaning can be found in a number of places, usually in back of the Blue Book of Gun Values, at www.oldguns.net
or at this STICKY
at Rimfire Central. If you go the the old guns site, just scroll down the left side to Manufacture Dates & click on Remington & enter the code. It'll give you the mfg month & year.