On a separate page you'll find the general information about the history of Keilwerth brass instruments  

There are serial number lists of Keilwerth saxophones around but there was no such thing for their brass instruments. Below you'll find a list of instruments and numbers that were traded through Ebay, Quoka and such, with information added from sites like Trompetenforum.de (where Brigantiumjazz triggered me to make this list), Trumpetherald.com, Trumpetmaster.com, Horn-u-copia and the Yorkmaster public pictures at Yahoo. There seems to be no relation whatsoever between the serial numbers of Keilwerth saxophones and their brass instrument serials numbers.

The serial number list of brass instruments with more than 650 entries, that's maybe 2 percent of Keilwerth brass production, shows a fairly continuous serie up to number 30654, with a few examples of every 1000. Then, after a few incidental Tonekings, new models show up, like the 2000 and 3000 series and the Student. The jump, first to the 100.xxx range, with mostly 'Student' instruments and then to the 200.xxx range with the 'De Luxe 2000' and 'Super de Luxe 2000' models could originate in other makers providing the instruments, as stated above. Here the gaps between the numbers are much larger. That's probably because they are part of a serial number list that includes the makers 'own' instruments as well as other stencils. And maybe also because these are newer and still with their original owners, so they down't show up on Ebay and other sites? Then there are incidental examples of the Modell AT and SX of which we don't know a number. La Sete and Hamilton instruments are integrated in this list, although they're not all made by Keilwerth, the La Sete instruments in the 15x.xxx range obviously come from Elkhart, Indiana.