I'm putting this in "General," ATM, because everyone interested in instrument history should take a look. I really need a new forum area.
This is a sampling of oral history of a variety of manufacturers from the manufacturers and folks associated with those companies. I'm just posting the tag for "German Music Industry," which contains videos from folks like the (recently deceased) former president of the Julius Keilwerth company, Gerhard Keilwerth. Keeping with the Keilwerth theme, there's also a video from Daniel J. Henkin, former president of CG Conn, King and Armstrong who imported Keilwerth horns and sold them as the "DJH Modified" horns. Use their search engine for much more.
Again, it's absolutely amazing what you can find on the Internets when you're searching for something completely different.
Edit: BTB, the G. Keilwerth interview is translated. He's also playing with a couple vintage horns in his interview.
Edit 2: This is for Helen: G Keilwerth picks up a Hammerschmidt and says that they copied Keilwerth with the Plexiglass keyguards. While obviously true, it's said in a tone of, "Those lusers over at Hammerschmidt ...."