I have an old Rock Island low sn (234434) "sporter". Looks like a piece that Townsend Whalen could have packed around . I am aware of the heat treat controversy .
Anyways , the bbl is marked , in the usual place with RIA above the flaming bomb and the date 6-13 below the bomb. My question concerns a marking on the oppsite side of the bbl (bottom) below the front sight band . It is stamped C 95 above the letter P .

Could one of you fellas please enlighten me as to the meaning ?
Thanks
Bob