Definitely look again because I didn't see a 'date code' stamp in any of your previous pics. Got to be one somewhere.

The 'T' inspectors mark is either Laenen Clement from 1952 to 1986 or Vostes Gustave from 1974 to 1988.

Given the other stamps it was probably Laenen Clement's mark.

But the 'AV' inspectors mark looks like the 'V' was stamped over it. The 'A' is probably Louid Croux Francois from 1951 to 1954. And the 'V' is Macon Isidor from 1929 to 1953. So looking at those marks it seems like your gun was built in the early 50s.