Dave, is that the same carburetor from
THIS THREAD?
My understanding is the "R" stamp in red meant it was an assembly line piece.
I've never heard that before and I've seen a lot of original carburetors without a red R, so I doubt that's correct.
But I'm also wondering if those base plates with the funky stamp are service replacements. It "could" be (not saying it is, but COULD be) some kind of inspection stamp for the base plate itself. Just another mystery we'll probably never figure out!
As for value, that's hard to say. It looks complete but worn, so it would have to be restored for sure, and that's going to cost a few bucks! Are you looking to buy it or sell it?
Ed