Well, I don't know about the legitimacy of this example, but that cigar, the Partagas Visible Inmensa does exist in that format. It's an extremely rare collectors item and if he can prove provenance and storage, should be able to get a pretty penny for it. The back story about it being made for the King of Egypt is not true, that's just a rumour that's been going around for a long time. In other notes, it is the largest habanos cigar.
It should measure 495mm x 53rg and is an official vitola, but these are extremely rare. Interesting to see one on a US craigslist ad. He must not know any serious habanos collectors as I would have thought if this were legit it would have been long picked up.