Personally, I'd start with a call to S&W customer service and see what they might tell the OP regarding the serial number. See what the config on record is. Next call would be to Simpson to see what they know about it. Perhaps they would pass the OP's contact info to the person they got it from.

A word of caution regarding labels. I know for a fact that at least some customer reps had the ability to reprint labels. It might not have been policy, but they had that ability. Aside from the shrewd forensic work pointing out the difference in the "3"s, if the work was done, as one suggested, by a S&W employee at the factory, is it still possible that the label might be authentic but reprinted to reflect mods? If so the factory info on the serial number might not reflect the factory mods.

Most fascinating pistol in this series that I remember seeing. And that's going a ways with Shoot Summ's collection.