TubeNet

http://cgi.ebay.com/GG-Conn-Piston-Valv ... 814wt_1139" target="_blank
If i had a nickel every time i've seen one of these, i'd be poor as dirt.

Or a piston "Trill" valve?

The Conn General Catalog 'C' pictures this horn and calls it a 'trill' model 10H or 11H depending on whether it's high or low pitch.