Leica Standard C, with 35/3.5 Elmar in nickel finish.
For the first two years of production the bodies were not standardized, the film plane to lens mount flange was slightly different. Lenses were usually engraved with the last three digits of the camera body they had been adjusted for, although some early sets have all five numbers engraved. Some cameras also have a swing away mask over the front of the finder.
The lenses initally offered for the Leica C were the 50/3.5 Elmar, the high speed 50/2.5 Hektor, the 35/3.5 elmar and the 135/4.5 Elmar.
The lens mount flange to film distance was standarized in 1931. The earlier cameras are described as being "Non-Standard", later models are refered to as the "Standard C". They can be differentiated by a "0" marked on the top of the lens mount on standardized cameras. Production of Non-Standards was 2995, although many have been converted to Standards. These cameras are difficult to find unmodified, and more difficult with two or three matched lenses.
The Standard C was produced until 1933, when it was replaced by the Standard E. Only 7231 Standard C cameras were produced.
Do you have a "C" or a "E"? The easiest way to tell is that the "E" has a pull up rewind knob.