So it's a repro XM16E1 then.
EDIT: Well, kind of, the E1 had a three prong flash suppressor when it was type-standardized as the A1, which later got the bird cage but no new designation. For some reason I thought the flash suppressor was changed in the package that added the forward assist.
When I was still a green buck sergeant in the early 80s we did have M16s, no A#, and XM16e1s, and even a rifle or two with chromed bolt carriers, in the arms rooms at Ft Lewis.