Best way to avoid scam, if you have even a hint of one, is not to do the deal.
Ditto.
I bough eight or ten 35mm from the FSU and they were all as described, but just before the craze for FSU Kit became a sellers market, and whatever could be posted on *bay was sent by 'scammers' as well as good, honest folks.
Look for a seller that has a long history on *bay, many positive reviews for camera kit, which takes some reading, and 100% rating.
Anything less than that, is a #arp shoot, IMO.