So, these are assembly line gauges; not something a field armorer would have...My mistake...
I was thinking these would be used to correct for sighting deficiencies...I know there were at least 3 different height front sights (from the CD blueprint); I was thinking if a Luger shot too low/high, you would measure the height of the sight and go to the next higher/lower...
...But I couldn't figure out the rear sight gauge...