So I recently got an early nikon F, 641xxx, and I purchased a a metered FTN prism off ebay because the prism that was on it is cracked. I just got it and it wont fit. I did a little reading and what I found is this prism isn't supposed to fit the early Fs. I was wondering if there was a way to make it fit, or if I just need to get a different prism?