Une réponse du Swatch Group, interpellé par le formulaire de contact du site Hamilton:
ils « tiquent » sur le cadran de la mienne
The case number 61007-3 was used for a SEA CLIFF III from 1970-73 and 61007-4 for the gold plated version.
But the dial design of the customer does not match our records as you can see below.
This could be for several reason. Maybe the dial was used from a different model or the complete watch is not original. Much can happen in 50 years.
Most likely the original dial was damaged and replaced with a different one. Hard to say. To be sure about the authenticity we would need to see the movement and customer dial for inspection.
Regarding the name SEA, we don’t know why this was chosen. But many different models had SEA in the name. Before 1970 over 50 different models were called SEA XXXX.
Et un doc non vu sur le net qui reprend la, large, gamme des Seaxxx

merci Hamilton
le modèle original de la Sea Cliff est bien antérieur d’une dizaine d’années:
