I've generally had good luck on Ebay. While there have been a few issues, mostly on things other than watches, I usually feel pretty good about what I've purchased. I generally shy away from certain things that I see as potential red-flags. For instance, when a seller conveniently (Or so it seems.) leaves out an important image, like calling something solid karat gold but not showing an image of the hallmark. I doubt that someone including the rather ubiquitous "rare" description gets too many to bite on it. Otherwise, we'd probably have a deeper market of buyers right now. But, then again, I suppose it only takes one.
For me it goes like this: 1.) Listen to that little voice. 2.) If seller isn't able, or won't, state clearly an answer to an important question, WALK. No, RUN. 3.) If a "watch guy" who one would think would be able to wind a watch as easily as you can, says, "I don't know if it runs", BOLT! Or allow for broken staff + in price offered. 4.) Go right to the negative feedback and check to see if there's a pattern of the seller doing something that would drive you nuts in the end. This includes rude responses to reasonable feedback verbiage, especially if feedback was "Neutral" not "Negative". 5.) Treat buying from some states in the US like the item is coming from Nigeria (I won't say which states, but I have my own experiences of perceived trends.). Like my brother used to tell me, "Don't put your head on something that looks like a chopping block." YMMV. Cheers all.