Both the F and F2 have their devotees: I have a beautiful black F which is so immaculate that it is doomed to be a shelf queen. It was an early model and is just a few numbers off being 6543210. Imagine the premium on that one(!) it did not have a red dot however, but was skillfully widened at the back of the viewfinder to accept the upgrade Photomic Tn meter. Probably ruined it as a collectable. So: 64 series carry a premium for being original, 65 series a premium for the old style "Nippon Kogaku" in a lens logo 65 red dot carry a premium for the dot which indicates factory built acceptance of the new Photomic. Apollo Fs have the F2 cosmetics(imagine Nikon produced the F and F2 side by side for a while... You would expect that from Leitz or Zeiss, but not the Japanese)

I still love my F: feels like a Contax IIa with a pentaprism