I have come into possession of a Canon rangefinder but I'm not sure what model it is. On the basis of various clues, including the shutter speeds available and the serial number, I know it is either a IIS2 or a IID2, but I can't tell which one. Is there some way to distinguish between these two?
According to this page, the IID2 has no flash capacity, while the IIS2 does.
The IID2, like the rest of the IID line has no flash capacity. Built through 1956, production was slightly over 16,000 units.
Like the IIF, the IIF2 has flash provision for bulbs only, the slow speed dial has no X on it. Unlike the IIF, this was a low production camera (2625), and was discontinued in Nov of 1955.
The IIS2, if you haven't already figured it out, has all of the features of the IIF2, but it also has an x-sych for electronic flash, marked on the slow spped dial. This was a popular model, with production of over 16,000 units, and discontinued in 1956.
Hope it helps.