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Jim and Ian, I think you are both partly right.
"The Canon FL 1200mm f/11 was a super-telephoto lens marketed by Japanese optical manufacturer Canon in June 1972. It was the longest super-telephoto lens in the Canon FL system. Canon did not release an equivalent lens for the Canon FD mount, so it remained the company's longest SLR telephoto lens for many years. It was eventually superseded by the autofocus EF mount 1200mm lens, which was introduced in 1993. The original FL 1200mm is now a rare and very valuable collector's item."
"The EF 1200mm f/5.6L USM is a professional L-series lens, that is now discontinued. The lens was first developed for the Canon FD mount, although never marketed until after Canon had transitioned to the EF mount. According to a Canon USA representative interviewed in 2009, the lens made its first public appearance at the 1984 Summer Olympics in Los Angeles; Canon had shipped five copies of the lens for media use at the Games. All of the FD 1200mm f/5.6L lenses were eventually shipped back to Canon in Japan. Later in the 1980s, these lenses were converted to the EF mount."
found hereand here