Usually the dust cover is missing on those things
It was in bad condition and I'd guess the bore was ruined
I worked on a '73 that had a SN 1007 which would make it a very early '74
They were tooled up in December of '73 and ran 126 (I think) rifles to give it the '73 moniker

When I need expert advice I tend to talk to myself
The older I get the better I used to be