An online guide to collectable cameras and related stuff
Canon Rangefinder Identification Guide
Canon III Series
The Canon III has the two peice finder magnification lever, and lacks the film speed reminder. It was discontinued in 1952 after a production of a little over 10,000. A small number of IIIs were marked "For Oscilloscope" on the back. These are rare, and if you have one we'd like to hear about it.
The Canon IIIA has a one piece finder magnification lever, and the film speed reminder. Produced until 1953, 9025 were built. There are IIIAs that were marked "US Army, Signal Corp." on the baseplate. These are also rare, and yes, please let us know if you have one.
You might be wondering why Canon made two cameras that were virtually the same concurrently. Maybe you're not, but I'm gonna tell you anyway. The III, like most of the older models has what is refered to as a semi-universal, or J-slop lens mount. The original threaded lens mount was a slightly different pitch than the Leica mount. During production of the S-II, the lens mount was changed so that it had sufficent slop in it that Leica or J-mount lenses could be used. The III has this mount, the IIIA has the universal, or Leica mount