One common definition of "transition embossing" is where a smooth base mold is retooled, drip points are added to the base plate and the Patent May 2, 1892 added.

I believe this is such an example. All the old SB 9's I have seen don't have an underline under the "o". I believe the ones with drip points without an underline are the "transition embossed" variants. I have matched up several of my SB molds with SDP molds which supports that theory.

While I have not (yet) tried to match this up, I suspect it will match one of them.

Thanks again to Chuck Alexander for getting me this variant.