SB or 5B or ??

Can anyone help me out with identifying what the characters after the 74 are?

I can't figure out if they are SB or 5B or 58.

Thanks!

Jim, I am going to take a stab for you... Gr. 5, class B. Oh, and thanks for the personal tour a few weeks ago when I was in town.

I'm thinking SB, but I don't know what it means. BS makes sense.

Attachment 251824

It's probably S/sedan B/ instead of B/Sedan...

Up till '68 the SCCA could class 911's in B/Sedan as well as C/Production

Thanks for the input so far. I know this car raced in the Trans Am series in 67 but in going through many historical photos I've come to believe the car must have raced with other organizations and that's what the extra markings are for. I'm leaning towards SB after seeing Curt and Chuck's post.

Scott, really enjoyed having you over and trading stories.

Curt, not sure if you knew this when you posted but the two cars in this thread were owned by the same person and have the same fender insignia (Erhard Motors and Erhard Motor Sales). The 74 car preceded the 54 car (it looks like #54 has a 1968 door handle).

Jim, I thought they might be related. I found internet photos of some 67/68 Trans Am races recently and thought that I had one of the 74.