The Leica IIIc, produced 1940-1951, was the most-manufactured screw-mount Barnack Leica with around 130,000 built, introducing the one-piece die-cast body shell that stiffened the camera and standardised wartime and post-war production.
It is a 35mm rangefinder with separate viewfinder and rangefinder windows, a cloth shutter 1s-1/500s (slow speeds on a front dial), M39 screw mount, and knob wind and rewind. Bodies are compact at roughly 450g.
The IIIc is the affordable entry into Barnack shooting: plentiful, robust, and the direct ancestor of the IIIf. Wartime examples with stepped or shark-skin finishes attract collectors, while post-war bodies are the practical users.
Check shutter curtains for pinholes, the rangefinder for a strong patch, and slow speeds for accuracy after decades without service. A recent CLA matters more than cosmetics; wartime production variations can carry significant collector premiums.