FrankS
Registered User
I think that I read that very early FED 50 (I-10) lenses had a non-standard thread. If I remember correctly, those early ones are valuable to collectors. Perhaps you could email Fedka or Oleg about it. I could be wrong.
My later I-10 screws in all the way no problem on my IIIa and IIf.
My later I-10 screws in all the way no problem on my IIIa and IIf.