unit id information needed

[Old Dodge Guy]

Well folks, it it getting close to the time to paint up the bumpers on my M38A1. I plan to use my dads unit markings from the Korea time period. He has come up with a great M38 photo with the unit markings, which I plan to use. I am having trouble figuring out the first letter/number on the right side of the bumper. it looks like: 6CP on the right------- 531 AA in the middle,--- and C2 on the left----driver side. Or it could be GCP on the right, with the other information the same. I am certain of everything but the 6 or G. Any help appreciated. I can't remember if he said Fort Bliss Texas, or Rapid City South Dakota. Definitely 531st Anti-Aircraft Artillery. 531 AAA. He was unsure why jeep marked with just 2 A's in photo.
BTW for anyone interested, the M38 hood number is very clear USA 2385908
I can't seem to get the photo to load, will try again later.
Thanks everyone!