Here's case number 39558, a Reference 2403 model, with the Landeron 13 movement, also circa 1939 / 1940.

As always, the last three digits of the serial number are marked at the corner closest to the balance wheel.

Let's stay on the lookout for these.

Jeff

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

: 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

:
:

: +++++++++++++++++++++++++++++