Zuanshi 钻石 SM1A shizhi 1

Zuanshi shizhi 1

Zuanshi was a longtime brand name of Shanghai Stopwatch Factory. Wristwatches with the slow-beat SM1A movement were introduced in 1969. This is an extremely rare example of one of the first. The 'S' on the caseback indicates that it is a prototype. It still has its original hang tag.