Slide 11: WWCo With Early Stem Wind

Another example of a good collectible is finding an early application of a stem winding M57 where the stem cannot be turned backwards and movement is key set. I'm still looking (slide 11 is not my watch - WWCo 597388).

There are a lot of stem wind M57s, and many look junky, but which grade and serial number range would have this (lack of) feature.

See paper and Additional Notes section of the tables. WWCo grade S/Ns 555,501-610 & 597,000-597,500 are good candidates.