Mr MShipley88 has talked about 'collecting creep' and here is an example... I have, almost by accident

, started picking up a few old D&D promotional mugs, and also those from other systems, like Call of Cthulhu.
But I know bugger all about them. Does anyone here? For example, did TSR do many of these? Does every Gencon do a promotional mug? Are there more rare or less rare mugs? Is there such a thing as a
MERP mug. Am I just plain weird?
Also of course interested in trade and purchase for said items. [would prefer them in a relatively clean state -- rather than besmirched with scrofulous stains from ancient gaming sessions...

]
Cheers!