Unertl Mount With Painted Arrow Question

Looking at Senich's books having 1941 sniper rifles, I noticed a couple showing painted arrows indicating which direction to raise the elevation. I've seen a similar but smaller arrow on a relative's of what I think is an earlier Unertl mount. Does anyone know what depot did this or if this a Philadelphia thing? The arrows look a little less profesional than what I think Unertl would have done. (see page 59 of U.S. Marine Corps Scout-Sniper to see a picture). Thanks in advance for any answers, thoughts, etc or if you want to see a picture of my relative's mount.

I don't believe the J. Unertl company painted any directional arrows on their scope mounts, commercial or military. Maybe just a field expedient mod so that direction could be determined at a glance. If Philadelphia USMC armorers did this, I think you would see it on a greater number of the USMC 8X scopes.

TW56