I bought a 286 motherboard from that guy (if it's the same one I'm thinking of artifact_systems) but I have become wary of him in the last year because he now lists his stuff as 'for collection only', which means he probably got some return requests in the past and now does not want to deal with them any longer. If you get something from him and it doesn't work, you'll be out of luck for getting your money back. There's a certain chip vendor from China who has done the same thing. As long as they list the parts as non-working, they can get away with it. If they list the parts as working and they don't, then ebay/Paypal will step in because they were dishonest from the start. Once you pay for it, your money is gone. You might get a working part, or you might get a part that is only good for gold scrap.
It is my fear that this may become a trend in vintage electronic items, where every seller lists his items as non-working just to avoid having to make returns later. Ebay/Paypal can't very well force a seller to accept a return of a non-working item if it is listed as non-working, though they may instead decide to ban non-working items from being sold on ebay if it becomes a problem with too many unhappy buyers complaining. Ebay always bends over backwards to make sure the buyers are happy even if they have to unfairly penalize the sellers and they don't have to. Ebay is the biggest online auction site in the world. It's not as if the buyers have too many other places to go.