Canon FDn 1200mm f/5.6L
I made a post a few days ago about built-in teleconverters and said that the EF 200-400 f/4L IS 1.4x was the first Canon lens with the built-in 1.4x teleconverter technology. While it will be the first production lens to have the feature, Canon did in fact make 5 lenses back in 1984 for the Los Angeles Summer Games in the form of an FDn 1200mm f/5.6L that also had a 1.4x teleconverter built in. All 5 of these lenses were shipped back to Canon in Japan and converterted to EF mount. These lenses then became the legendary made to order EF 1200 f/5.6L without the built-in teleconverter.
If you've never heard about the super rare Canon EF 1200 f/5.6L, Bryan at TDP has a great article about his time with the lens. Read it here..
Thanks for the heads up Phil
cr