I just got my first Speedmaster Pro, a fine timepiece from 1973 or '74. Works like a charm!
I was very surprised to find out that Cal. 861 does not "hack" (i.e.: the seconds hand does not stop when the crown is pulled).
Furthermore, just like with Cal. 7s26 in my Seiko diver, it still is possible to stop the seconds hand, or even reverse its course, by turning the pulled crown counterclockwise. That is a way to adjust the watch to the closest second against a standard timekeeper, such as an ntp server, or an atomic clock.
My questions about this are:
1. Can anyone explain how this happens in the watch mechanism, or point me to a reference about this?
2. Can this practice of stopping or reversing the seconds hands damage the movement?
Thanks for your thoughts.