Horology glossaryDefined term / watchmakers-mark
Watchmaker's Mark
A small scratch or stamp a servicing watchmaker leaves inside the caseback, recording that the watch was opened and, sometimes, by whom or when.
Authentication note
Why this detail matters.
Watchmaker's marks form a rough service history when several are present, and their total absence on an old watch that claims regular servicing can be worth asking about. They're a minor but genuine data point, not proof of authenticity on their own, since a caseback carrying marks could still have been swapped from another watch.