If its platinum, then try to sell it here. There may be, (cough cough) members looking to acquire a little platinum.
Detecto, first of all, subsequent sales are NOT through eBay. Second, I have 100% perfect Feedback over 2000 (95% from SELLING) so I don't really need any reminders of what to do or how to do it. Thanks anyway! Over the years, I've watched eBay turn from something that was FUN into a tough slog, uphill all the way, totally biased against sellers. That's when I quit listing anything other than cheapo items. On the other hand, it's where the buyers are, and there's plenty of buyers for low-priced material.
I would at least call that company you won the coin from and see what they would pay (certainly they can't dispute the grade LOL) -- they don't care where their "supply" comes from.