Watch & Clock Case Marks

What is a Case Mark on a Watch or Clock?

When a watch or clock is repaired, horologists stamp or scratch a system of small letters and numbers inside the back of the case. This records who has worked on the timepiece and can be used to correspond to records at the repair shop. Although each business has their own record-keeping system, these records could describe what actions were taken to fix your watch or clock, the ownership of the piece at the time of repair, etc.


The American Watchmakers-Clockmakers Institute is the only repository for watch and clock case marking information in the U.S. We have issued over 5,500 case marks to date. We will provide case mark information in two instances:

1) To our members to help them identify prior repairs, and
2) To law enforcement in the case of theft or forensics investigations.