Unconverted pre-1977 Nikon lenses that can't be used on modern Nikon cameras may still be usable on other cameras with a mount adapter. I haven't tried using a 1960s Nikon lens on a Canon camera yet, but I have used late '70s and 1980s lenses (AI and AI-S type) successfully.
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http://www.nikonians.org/nikon/slr-lens.html
http://www.kenrockwell.com/nikon/compatibility-lens.htm
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Got bored with digital and went back to film.