Hi Seiji
Not sure if you already found your answer (With all your knowledge on Longines and all the research you're doing I guess you already have some information
😀), but I'm sharing what can be found on a French source that I personally like reading articles from :
https://chronographes.net/2018/05/12/longines-mn-ref-5774-dans-lombre-des-stars/
Basically it is said to have been ordered following 2nd world war by the military French Navy and delivered between 1946 and 1948.
And to your point, it was supposedly then for officer only :
In French : "Qu’on ne se méprenne pas pour autant : la montre que nous présentons aujourd’hui n’est pas un de ces modèles qu’on appellerait aujourd’hui « tactiques », c’est-à-dire conçus pour les opérations d’infanterie de marine voire pour la plongée de reconnaissance ou de combat. Pas du tout. Destinée aux officiers de marine, elle devait cependant supporter l’humidité, résister aux chocs, être lisible, fiable et d’une précision sans faille. C’est ainsi, sur un cahier des charges grosso modo bâti autour des ces critères, que la Marine nationale passe donc commande à la manufacture Longines d’une montre à cadran et aiguilles lumineuses, boîtier acier, fond acier vissé."
Google translate (sorry I'm lazy) :
"Let there be no mistake: the watch we are presenting today is not one of those models that today we would call "tactical", i.e. designed for military operations. marine infantry or even for reconnaissance or combat diving. No way. Intended for naval officers, it had to withstand humidity, withstand shocks, be legible, reliable and flawlessly precise. It is thus, on a specification roughly built around these criteria, that the French Navy places an order with the Longines factory for a watch with dial and luminous hands, steel case, screwed steel back."
Have a good weekend,
And thanks for all those posting those watches. I don't own one but the more I see them the more I like them.