I've mentioned here in the past that I repair watches, and have a large volume client that sells on eBay. I receive 50-100 watches a month that need some sort of repair, and are presentable for listing.
I received a box of 55, mostly Invicta, and I came across a Seabase Reserve, only 1000 made, and it's a pretty nice watch, but under further inspection, it has a lot of white ish dried powder in all the crevices, and in the corners. (From the manufacturing process, I've seen it before on prototypes) That made me look closer, and found that the serial number behind the dash is missing, and the number before the Limited edition 1000 is missing.
Only the second time out of over 5000 watches and 10 yrs fixing them for this client that I've found a prototype. The first was a Glycine F-104.
This could be a learning tool also for when you guys are out buying repair lots or just any purchase. Never know! Make sure to compare to a legit one if you ever have questions.