Finally, I got my copy of the 21/3.4. Should had bought one 2 years ago, their price is just getting higher and higher and if I don't get it now, there is no way I can afford one in the future. Mine is a late copy series start with 26xxxxxx. On the web, many site stated that the late copy had been modificated to fit the M5 and CL. Well, I was trying to fit it onto a CL, but it wasn't the Meter arm that gets in the way. It is actually a piece of plastic behind the focusing coupling that is blocking the rear element. If my measurement is correct, there should be 1mm between the rear element and the
Meter arm. There will be some butchering done tonight.
edit:OK, measurement is a bit off by another 1mm, I think I got a good reason to get another camera.