Should just lock the post and require him to send verification of who he obtained the keycap from to mods before allowing discussion to continue. And if he doesn't provide it, drop an IP ban on him and delete the thread.
I'd say if Belfong isn't aware of a gr8est collector from his own country, we can pretty much wrap this one up anyway though (as they'd have crossed paths at some point).
edit- on second thought, if no verification then maybe change thread title to this is a scam instead of deleting it, and a mod can bump it daily so that no one stupidly buys it (though might be able to report to ebay as counterfeit goods and get it killed, idk how that works though).