The number of technological advances introduced by Zeiss in the Type III is indeed long although it is difficult to fully appreciate just how advanced they were by 1936 standards. 

The ability to change shutter speeds through the entire range before or after advancing was an important feature as was the uncoupled light meter.  The bayonet lens mount was continued in both the II and III having been introduced several years earlier in the first Contax model.  However, professional photojournalists still preferred the Contax II without the light meter perhaps because of the additional size and weight, but more likely because of the limited utility of a light meter mounted on the camera.