I've run into company that used this before. Revit Fabrication Parts broke their use if it. This field is automatically assigned in EST/CAM but when importing something from Revit, they all seem to be set to Zero with no way changing it (last I checked...it's been a while).
Depending what your purpose is, if you need a unique ID, the GUID's may be a better option but there's also been some issue with GUID's not being handled properly too in some prior versions of Fabrication and Revit.