You guys do have a Cessna issued serial number specific POH I hope ?
I would be very surprised to see a serial number specific Flight Manual for a C152, I don't recall ever seeing one, I think they were generic back then for the small Cessnas. Any weights quoted in the Flight Manual would be generic in any case.
However, what is relevant, and could be expected to be with the aircraft would be the original Cessna factory weight and balance. It's usually in a wad of weight and balance documents stuffed in a pocket somewhere. A rainy day review of that document, and the subsequent W&B revisions can produce surprising information. Do they pass the sanity test one to the next? Would it appear that what was changed from one revision to the next justifies the change in weight stated?
That's where I see mistakes, typos and transposition errors much too often....