Fuselage skins

Good day to all! I have a 1960 Forney with 670 hours ttaf. It has an 0-200 with 360 hours smoh. I believe that the low time is due to some obscure damage where the repairs are listed by fuselage skins called out by part number. One being a belly skin, one right side boot cowl. Only one of the part numbers listed shows up in the Forney parts catalogue. Is it possible that the numbers listed are an aftermarket vendor ( which I doubt existed) ? Any help would be appreciated. Thanks in advance. Mike. (Frank’s brother and co owner).