It has been a few years since I started this thread, but I’m not one to give up!

I decided to polish the old horn up and start digging again. I actually never quit, but researched less often. I did discover 2D engraved on both the upper and lower joints under the keys. I did post on a Facebook clarinet group asking about any info on the maker. A member posted that it was a Malerne stencil. I haven’t been able to find a malerne stencil with the double register linkage similar to this horn. There are some other differences that I have also noticed. Not that the member is incorrect I’m just open to any other thoughts.
I’ll post a couple new pics