I noted a hole on the left side of the front of the receiver that looks like someone drilled two holes close to each other and then filed them into a single opening.
I initially thought that this was a modification that the gunsmith who sporterized the rifle had done to accommodate just such an eventuality.
Now, after looking through a lot of pictures, and seeing the identically shaped and placed hole on several Spanish rifles, I suspect that it was actually done using a single jig at a Spanish armory.
