What's that lens? (Identifying a 2.8 Tessar)

I've been "given" (I paid €120 for it, so it's almost a gift!) an Ahel1245 enlarger with a Componon-S 150mm and a few other things.

Among these things there was this lens, partly disassembled, and I don't know what it fits or what it's worth...

It might help if you show the lens mount side also.