GG, What's the bayonet swivel lock/tab look like on yours? Mine is a spiker so's I figure the stock is a replacement - unless the FSG or the barrel isn't the one that came with this thing.
Long collar barrel and blade bayonet, My stock is matching number side sling swivel, but yours does look scrubbed. I can faintly see parts of numbers behind the sling swivel on the stock. Whether done at arsenal level or States side who knows.
Everything else on yours looks the same as mine, U stamped rear sight leaf, long collar, milled FCG. Check your lower stock ferrule to see if it is V notched or U notched.