Helen, it doesn't look like you have any D&J horns with the "Julius Keilwerth" stencil name. I haven't looked through all the rest of your stencils, but are there others with the "JGK Best in the World" stamp?
Nope, never seen a D&J engraved Julius Keilwerth. Nor have I seen a Best In The World stamp, but... Here's the thing, the JK logo on the back looks wrong to me. I have never seen one that was hand engraved. They are all perfectly uniformly round. The one on this horn looks "off" to me. It looks like it might have been hand engraved.
Here's what I suspect happened, I do have a couple examples in my gallery of unstencilled D&J horns, I suspect someone got their hands on one of these, and turned it into a "Julius Keilwerth" alto. Then at a later date, someone else either tried to cover that up by buffing out that stamping a bit. Or, the photography really is that sucky...
Regardless, the lovely engraving was done later in the horn's life, after it left the D&J factory--waaay later.
Of course suspicion is not fact. And I cannot prove suspicion. Whatever the case, there is nothing about the horn that is remotely authentic JK. Having said that, it could be that it is one of the horns that JK got when they took over the D&J plant. However, even that doesn't jive, since the serial # isn't late enough in the production run to put it close to when JK took over D&J in the late 60s.
BTW, I have done the point to point comparisons between JK & D&J. You can find the illustrated info on that, and all you ever wanted to know about the German stencil horns on the
brand's page on my website.
I should be kind and put some anchor tags and a navigation tool at the top of the page some time like I now do on all my brand info pages. Once I'm on the new server, I'll do that on my D&J, Hohner, etc pages that are packed full of info.