I have owned several originals with rank insignia under the collar. Usually this is done when there are not painted or leather rank insignia on the epaulets to denote rank. Metal insignia on leather epaulets and parachute straps/seat harness were not a good combination so fixing rank insignia under the collar solved this issue.
A bit late about this, but how do you fix a rank insigna under the collar without going through the leather on both sidesand still have it permanently attached?