/fa/ - Fashion

Hands in an accutron watch are made of magnetizable material, and so can affect the timing of the tuning fork when they pass by it (i.e., when they pass by 12 o'clock), and have a measurable impact on the rate of the watch.

This is similar to the reason accutrons will run off spec if they're regulated with the caseback off - the caseback changes the magnetic properties enough of the watch to push the watch timing by a few seconds per day. Accutron service manuals include the offset required for the various movements.