I forgot to also add in the last posting, that there are no dumb questions, only dumb answers.
Anyway, now that AMG is owned by MB, yes, there should be a starmark and a part number on all OEM parts, AMG included.
In fact, very often, when MB out-sources a part (and there are a lot of them, since they buy lots of parts from the same places that Porsche and BMW but their parts), MB , as well as the others, will add their own part number, either on the casting or as a sticker. Don't forget, all manufacturers need to have their parts conform to their own numbering systems.
But no, probably this would not be enough. Even cigars are being counterfitted nowadays, so it never hurts to buy things from reputable sources. NEVER TAKE THE WORD OF ANYONE ON eBay OR ANYWHERE ELSE, THAT YOU ARE GETTING OEM PARTS. INVESTIGATE!!!!!!
And don't forget those famous words of the Romans thousands of years ago - "Caveat Emptor, let the buyer beware". I guess scams have been around since Day One.....Andras