Damaged alternator pulley

Good morning

I have taken my car to an acquaintance to change the. Distribution strap and pump. During the disassembly, it seems that there were complications for being too hard, and in the struggle they have damaged the alternator's pulley.

He tells me that nothing happens, that he will put the same piece and it does not matter, but I do not trust me ... can you tell me if he can give me a fat breakdown to install this piece as seen in the image?

Thank you