35mm SLR · 1971–1990
Canon launched the FD mount in March 1971 on the professional F-1, and it carried the FTb, AE-1, AT-1, A-1, AE-1 Program and the rest of Canon's manual-focus SLRs. Original FD lenses lock on with a breech-lock ring you turn while the lens stays put. New FD lenses from 1979 mount by twisting the whole lens like a bayonet, and they fit the same bodies. Canon moved to EOS and the EF mount in 1987, and the T60 of 1990 was the last FD body it introduced.
Older Canon FL lenses fit FD bodies but meter stopped down, and R-mount lenses also need manual aperture. FD lenses don't fit EOS bodies. Canon briefly sold an adapter with corrective optics for certain FD telephotos, and adapters without optics badly hurt image quality.
6 cameras we cover.

Canon · 35mm SLR
Battery neededCanon FD mount · 1976–1984
$150–$220 typical ask
209 on eBay

Canon · 35mm SLR
Battery neededCanon FD mount · From 1981
$160–$240 typical ask
175 on eBay

Canon · 35mm SLR
Battery neededCanon FD mount · 1978–1985
$170–$310 typical ask
214 on eBay

Canon · 35mm SLR
Battery neededCanon FD mount · From December 1976
$110–$200 typical ask
94 on eBay

Canon · 35mm SLR
Meter onlyCanon FD mount · 1971–1981
$230–$410 typical ask
124 on eBay

Canon · 35mm SLR
Meter onlyCanon FD mount · 1971–1976
$85–$180 typical ask
185 on eBay