Stop-seconds (hacking)
Stop-seconds, often called hacking, pauses the running seconds hand while the time is set. It allows the display to restart in synchrony with a chosen time signal. This differs from stopping a chronograph measurement, where the timing hand can remain stationary while ordinary timekeeping continues.
Operation depends on the movement. Longines describes time setting with stop-seconds for calibre L688 by pulling the crown to position 2 and returning it when synchronised. Seiko's instructions for the specified V calibres use the second crown click, at which the seconds hand stops where it is. Different numbering systems for crown positions are one reason to follow the appropriate manual instead of a universal sequence.
Stop-seconds does not mean that the hand automatically jumps to zero, nor does it guarantee subsequent rate accuracy. For an older watch, establish the function through calibre identification and documentation. Do not assume every watch of the same brand has it. A sales description should distinguish a documented, checked function from an inference based on modern models. Never force the crown or hands to obtain a stop.
