I think that was an early version for the OTHG So Calif Street Rod Assn (SCSRA). They also had a plaque that dropped THE and replaced SCSRA with San Diego. There are several versions for different chapters shown on this page near the bottom ... https://carclubplaques.pairsite.com/SameNames/SameNames.htm
I can check with Craig Lake too. There was discussion of Dago and Berdoo being within some sort of umbrella organization....which was/is odd - as the club was originally conceived as the "anti-club" do-your-own-thing no-red-tape-bs organization.
This car club plate was created in the 50’s—early 60’s by a deceased friend of mine. I was not old enuf(now 75) to be an actual club member, but when I bought a friends 56KH Harley back in 1978 he “gifted” me with an extra that he had. I only know of three of these around and rumor has it that it was sand casted in the local high school shop class.
The Jalopy Journal
