ZRC produced diving watches from 1950-1975 with mainly 3 series. Heard that ZRC supplied watches to the French Navy, Paris fireman, military corps (Marine Pompiers de Marceille).
Below is a near mint condition Spartiale ...series 3.... There are two versions namely the Spartiale with 25 jewels and another Le Jour ZRC300 made for the US in 17 jewels... This is a day date version measuring 38mmx50mm with sunburst blue with a purple hue to it. It has a very unique cuff style bracelet which is surprising comfortable to wear.
There are two versions