*long time lurker*
FWIW I too have an early(serial no: 1911) Longines of a similar design, only in a man's size. I'm afraid one of the better photos I have of it, alongside a silver cased "trench" from 1916 and a railway issued PW from the late 20's IIRC.
Nickel cased snapback. It came to me in a bit of a state. Blackened with the years and the dial had more dodgy hairlines than a wig convention. Luckily I was able to source a near identical replacement, the only difference being the Longines script was written in the usual place under the red "12" on the original.
So it seems Longines were producing wristwatches including men's wristwatches earlier than was thought. Or they used older movements when the trend started to take off? Though one would expect radium dials and hands aimed at the men's market(they didn't come in until after circa 1913 IIRC).
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