So I found a rotary valve trumpet on Ebay--quite expensive for a Chinese horn--which has "Wiener Klappen." Now, my first thought was "A shot of penicillin will clear that right up," but it turns out that "Wiener Klappen" are a type of valve. The trumpet has three keys which look like water keys, but can be activated while the horn is being played. I can't post a direct picture, but its described on O'Malley Brass's site:

<LINK_TEXT text="https://omalleymusicalinstruments.com/s ... y-trumpet/">https://omalleymusicalinstruments.com/shop/rotary-trumpet/omalley-vienna-rotary-trumpet/</LINK_TEXT>

What I can't figure out is that thumb valve. It appears to simultaneously extend the first valve slide, and change the position of a rod that runs under the levers for the two Wiener Klappen, but I can't figure out why it would be necessary to move the position of that rod. Any ideas?

OK--I figured out the thumb valve. It simultaneously extends the first and third valve tuning slides. Actually, pretty cool if it works.

I can't imagine that opening up a hole in the tubing would do much for your tone, even if it does allow for better intonation.

Wrong forum. I think there's one called Trumpet Angel Heraldry or something that exists somewhere.

According to Dr. Jack Burt in the video below, the key makes high notes speak better and easier.

<YOUTUBE id="0ziwwRhqgqk">https://youtu.be/0ziwwRhqgqk</YOUTUBE>