Ich hab' folgendes bei secondtimeround gefunden:

The last major changes to the manual wind chronograph came in the late 1970's when Rolex introduced the 6263 model. This was the first model to have truly waterproof pushers. The earlier Oyster Chronographs had simple round pushers with internal gaskets as the only sealing mechanism.

Das geht ja wohl einiges nicht zusammen.

Sach ich jetzt mal so...

der
"Butch"