The P and J defiantly have different machines with the Js appearing just to be a larger version. The Js stand a lot higher than the p, their back plates are a lot larger and the posts look roughly a 3rd larger than the p to the eye. I've just put both serial numbers into guitar dater project. It gave the p as 1997-2000 and the jazz as 04-05 both made at fugi-gen. The J is 60s spaced with 60s headstock logos, CAR with matching headstock and 3 ply White plate and a dots and bound neck. The original bridge had threaded saddles. It weighs very noticeably more than the p. The P has television logos and is Olympic white with a black 3ply plate, non threaded saddles. Both are strung over. does this help at all?