Hey Robot,
In a way I am extremely happy for you that you may have this opportunity, and on the otherhand, I know exactly how stressful, time consuming, and nervewracking this process is. Your worries put you right in the center of a fork in the road, either you pay tons of money for a fake, or let go the genuine article for differences that are negligable or unintentional by the original prop team!
I also can appreciate the advice of the others in the thread. There are a lot of fakes out there, so we HAVE to stick together as a community if we have any chance of keeping our hobby a positive experience.
Can't help you with the pistol, but I am glad it seems you are asking the right questions. Good luck.