Interesting that they were keeping the case-backs matched up with the cases . . . gives new meaning to the phrase, often used in the automotive world -- "matching numbers".

There were other models that had these kinds of markings in the late 1930s; I can check the files and try to add a couple of additional samples.

Jeff

+++++++++++++++++++++++++++++

: I like how the punches for the serial on the caseback were clearly
: done manually - the lack of alignment reminds us of how things
: were before watch manufacturing became as industrialised as it
: is today.