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I love happy endings!!!
cool militaria
Semper Fi
Phil

You're welcome. I did find another command pilot wing made by SUSCO on eBay and they are the solid back type wings . Totally different look.I'm on my phone heading to San Diego and can't cut and...

Bingo!!
S21 Susco/Harry Sugerman Inc., San Antonio, TX
1318249
FORT POLK DENTAL ACTIVITY DISTINCTIVE UNIT INSIGNIA

1318253

Semper Fi
Phil

It very well could be. I have to correct myself and say that they used Alpha-numerical codes.

With that I did find this.
Harry Sugerman/Susco. (S21)

But this is just a search of maker mark...

I agree with Gary. Manufacturer's went to numerical markings post WW2
I tried to find the maker but had no luck with the 5-21 marking.

Semper Fi
Phil