That is the bottom of the CPU, you could in theory count the contact points and the contact type and get somewhere in the right socket, past that nope.
The other side of said CPU, if cleaned from paste, would tell the type in plain text format.
I would require the seller to declare CPU type while selling it and/or providing picture of the top with said type shown.
the bottom being nice, shiny and clean doesn't really tell anything more than that of CPU.
Edit: of course seller wants CPU type to be mystery but... that is a gamble in and of itself, I'd stay far from such sales. Especially since CPU type affects price a LOT, be it low, high or good pricing.
it being a mystery makes "price is fine" completely the choice of seller.