CHECK THESE OUT! The THREE Leica M3 versions.

The Leica M3 is a classic 35mm rangefinder camera. From its introduction in 1954 and the last model made in 1966, Leica had made the M3 for 12 years! During these 12 years, there are some changes made. These three versions kind of summarize all the changes. Since there are a lot parts that are interchangeable, there is a chance some custom ones that are assembled with different parts. For example, some of double stroke models got "updated" to single stroke, so the camera will have both double and single stroke features.
My personal favorite is the original double stroke model, although I really do like the other two models. With Leica M3, there are no bad choices!