The "vocal" version of the Wonderphone cornet has markings etched on each valve slide for positioning in C, Bb, and A.  The leadpipe slide is used for changing between high and low pitch.  This horn is silver plated brass with a gold wash bell.

 

Although it is only an "S", or small bore, this cornet both plays and works so well that I have no idea why Conn built Wonderphone cornets for only a handful of years at the beginning of the twentieth century.

 

In the first photo it is shown outfitted for C in high pitch.  The second shows a Bb configuration in low pitch.  I found this instrument in the basement of a music store in central New Jersey.