:Hello
Thank you for your answer.
I'm going to make some pictures, even if the forum image upload conditions are a bit

Heuer Camaro,
Handwrist, no watch strap ( I remember that I used lots)
Stainless steel, black,
2 registers, seconds on left, 30min on the right,
Blue second timer in the middle.

Numbered c-42397 behind, and no.135224 on one side.
bought in 1971 in Basel. Switzerland.
All Oiriginal parts!
An still running...
Needs cleaning and servicing!