Mark or tag material with proper job number, piece marks, and other identifying marks as required. (copymyresume.com)
In other instances, parts may be sanded down to remove the existing part number, date code (which indicates when a part was made) and other identifying marks. (scientificamerican.com)
There are some other identifying marks of a healthy relationship which Cloud and Townsend mention. (adultfindout.com)