OVERVIEW
Original ID Field is a special field, which displays the Original ID of the Work Item. The original ID field is useful to know information about the work Item. Users can add this field from Field Layout.
The original ID Field is helpful when we work with Branched Items in an Advanced Version of the Project. On Branch, a new ID is created and displayed in the format of Workitem_Code-New ID(Original ID)
ORIGINAL ID ON WORK ITEMS GRID
The Default value of the Original ID is 0 for all items which are not branched