(Helen) I am very curious about this stencil. With its New York skyline, and stylized typeface, it most definitely tries to bring an American vibe to the table. Both the alto and tenor shown here (so far) were made when the Keilwerth factory was still in Graslitz. 

Although the serial number chart is not accurate for these pre-Nauheim horns, we are looking at something rough circa 1942.