I've seen that on several models, mostly Admirals and the later Conquest dive style watches.

 

... or on some chronograph "water resistant" with 30CH inside.






Ciao,

Giuseppe.

 

Yes, and even Valjoux 72 (Longines 33x) watches from the late 60's and 70's.

 

.........

Ciao.

G.

 

.... what do you think on this power reserve?





Giuseppe.

 

I like it. It rather reminds me of the mystery dial.

 

The lugs look good, the dial and hands are correct.... only the crown is a replacement. That might be a period correct Longines bracelet too but I'd have to see the clasp.

 

Well, that means it probably was available in the 50's.