eBay is a watch purchasing minefield, but eBay authentication has all the value of a faulty mine detector for negotiating it.
Smoke and mirrors
https://pages.ebay.com/authenticity-guarantee-seller/
Only one opinion, but I place no value in eBay authentication, not in the experts, not in the process. I've searched eBay for a description of its authenticating "experts" and have uncovered no reassuring detail on who these "third-party authentication partners" are and what are their qualifications. I am awaiting delivery of a simple Seamaster 30 eBay purchase that apparently managed to slip under eBay's authentication radar and for that I am happy. "Buyer beware" offers more comfort to even a non expert like me than does an ill explained, haphazard, yet overly promoted "song and dance" arbitrarily administered by eBay.
This entire page distorts more than it clarifies.
https://pages.ebay.com/authenticity-guarantee-watches/
We'll just pick on the eBay experts.
"eBay has partnered with leading industry experts whose services and capabilities have been thoroughly vetted. The authentication partners are leaders in their industry, with years of experience, brand certified watchmakers and technicians, using advanced technical equipment in a state-of-the-art facility."
How does this partnership arrangement work? What describes a
leading industry expert? I mean ... as opposed to a mere
following expert? How were the experts thoroughly vetted? What is deemed to be adequate years of experience? If they're leading experts in their industry then shouldn't they be too valuable and too busy elsewhere to bother doing mundane work of inspecting used watches for eBay? Do eBay customers get to see watchmakers' and technicians' certifications? Do the customers learn the name of the expert who "certified" their watch or or they faceless experts? What is this technical equipment and how advanced is it? How advanced does the equipment have to be for such a superficial physical authentication inspection as is described? State-of-the-art facility? What is that?
"Can I choose to not have my item authenticated?
No."
What's to keep a bidder from couching a message in the form of a question to an eBay seller agreeing to bid to buy a watch on condition that the seller will send the purchase directly to the bidder, circumventing the obstruction that is the authentication process? It's certain that dire things would happen to a seller's ability to sell on eBay if any such arrangement was detected, however I didn't find any fine print describing provisos against it.
This is just Ebay nannying and I won't be nannied. I particularly don't want Ebay's "experts" getting their grubby little paws on any watch purchases I might make. It's also additional cost, wasted time, and risk. If I'm denied the option to take my chances with my Ebay watch purchases then I simply won't buy through Ebay anymore. I'm sure they're not going to miss little ol' me anyway.