From what little I can find, I am reasonably sure that they are legit. Take a look at the seller's other items and it seems they are selling decommissioned servers and industrial equipment.
I doubt the vrms on my board could handle it, but any x79 based board that had any kind of overclocking headroom should have enough power to run one.
The seller had another auction where they were trying to sell them in a pair, and in that auction they had a pic of the bios screen.
2x INTEL BLACKOPS 6 CORE 4.60GHz 2011 Socket Engineering Sample CPU A19