M7 bayonet model FZR
FZR is an unknown maker, but may be Frazier Manufacturing Company according to M. H. Cole. The M7 bayonets marked FZR were Vietnam War era and saw service there but there are no government procurement records for FZR.
made by Frazier 1966-1971, app. 260,000 made, this info, again, is from American Bayonets of the 20th Century.