According to Marc James Small
"Several of the early Canon lenses would not mount on Leica cameras, which came to light with the flood of Leitz-equipped photojournalist who poured into Tokyo at the outbreak of the Korean War. Canon adapted the correct 39mm x 0.977mm mount in 1952 and used this on all cameras and lenses made by them until the end of thread-mount production in the 1970's, though the camera flange design differed slightly from its German paradigm."
That silly Branack threw a little curve ball there not making the thread pitch a full 1mm.
You can ID the lens you are looking at here.
http://canonrangefinder.servehttp.c...er/index.php?page=lenses&type=standard_lenses
"Several of the early Canon lenses would not mount on Leica cameras, which came to light with the flood of Leitz-equipped photojournalist who poured into Tokyo at the outbreak of the Korean War. Canon adapted the correct 39mm x 0.977mm mount in 1952 and used this on all cameras and lenses made by them until the end of thread-mount production in the 1970's, though the camera flange design differed slightly from its German paradigm."
That silly Branack threw a little curve ball there not making the thread pitch a full 1mm.
You can ID the lens you are looking at here.
http://canonrangefinder.servehttp.c...er/index.php?page=lenses&type=standard_lenses