The squared off (non beveled) nameplate was for the standard prism finder.
I had this same issue.
Luckily I had a parts body that had a beveled nameplate and I swapped them.

There was also a mod to the mirror box component that allowed FTN meter finders to fit. There is a ridge on the top of mirror box that prevented the FTN finder from mounting on ealier bodies. This mod happened around '68 I believe and is designated by the "red dot" bodies at first. They later dropped the red dot as all bodies had the new style mirror box.

Go here
http://www.destoutz.ch/nikon-f.html
if you don't have the time hopefully someone (John) with the exact info will reply.
I don't know if earlier Photomic finders fit the old nameplate and un-modded mirrorbox.