Thanks everobody !!
About the movement, thanks to
@dodo44 and
@DirtyDozen12 for you informations, finally it seems to be a 27MS rather than a 10.68N or 23M (see pictures below)
27MS
View attachment 498410
10.68N
View attachment 498409
23M
View attachment 498414
Happy to have confirmation the watch seems all original

About the case my doubt was about the fact there is no Longines engraving on the caseback because I have seen some case made by PGF with the Longines engraving like this one :
View attachment 498420
(credit : Arno on a french forum)
To
@Fost : yes it's a 35 mm
Click to expand...