TromboneChat

I was looking at a Conn with a serial number of GG 770###.

According to the sources I looked at there were GA prefixes in the lates 70s but I didn’t see any references to GG. Can anybody explain?

The vendor thinks late 50s but I’m pretty sure that’s wrong.

Certainly not 50’s prefix letters started early 60’s and the GA early 70’s

70 serials 1977

Maybe post some photos and that will help identifying it

According to the Conn Serial Number listing, the 1977 instruments were numbered GA700000 and up.
1978 started with GA800000.

Could the "GG" be a typo or a misreading of what's stamped?

I see Dillon identified a couple horns as GC and, I think, GJ.