Have you tried separating the chip from its heatsink? As junk said, the model number should be printed or etched on the package.
That said, I don't remember if there has ever been a desktop CPU with an island of pins/pads in the middle like this as that area is usually filled with bypass capacitors on the motherboard and under the die. A group of ground pad in the middle like this is typical for BGAs and in that case, a used chip ripped off a board would be nearly worthless as very few people are capable of swapping out BGAs and even fewer would buy chips of unknown origin that have already been removed from their original board.