What about it doesn't look 'right' to you?

Looks like a normal #35 that attached to the bolt release box on a Mauser.
The top bar has the dogleg in it , but that was the just the standard style bar for the sight.
I think this sight was just made for the Mauser.

A #34 was made for the 03 Springfield, Krag and Lee Enfield.
#36 for the M/S, Mosin Nagant & GEW88 type sporters,etc.

I don't recall ever seeing that keyhole shape cut before.