Like yours, mine is also Ref 5080.
Until I found mine, I was only aware of Ref numbers 5420 and 5418, with 5420 is the two-tone case like the 5080 while the 5418 is an all steel case.
They are quite rare and hard to find, but actual production numbers we don't know. They are dated around mid 40s but probably have been in production for a few years.
Caliber 91 is the correct movement for this watch. There are quite a few rectangular GPs from that time period with that caliber, so this one is relatively easy to find.
Best,
CC