Date: Unknown. Owner unknown
The New York Wonder in C, Bb and A, or "Wonder Solo Cornet with Vocal C attachment" as Conn called it can be tuned in C, Bb and A as the name indicated. The removable section of the leadpipe, with the mouthpiece in it, can be plugged into either the Bb tubing, or into the "C attachment" as is the case in this picture. There are also two main tuning slides; the one above the instrument in the Bb/A tuning slide. The main tuning slide on the instrument is the C tuning slide.
The common name for this model is "New York Wonder", which apparently stems from the fact that it was sold at Conn's New York store. You are liable to see these in a variety of bore sizes ranging from "S" (small) to "L" (large). Often this bore size is stamped on the 2nd valve.
What Conn said in 1887:
The cornet player who desired to use his instrument in the church choir or with the Piano or Organ and not be compelled to transpose the music, but play it just as it is written, will find this Vocal "C" attachment an invaluable adjunct to this instrument. The cornet in Bb and A is positively the same as the Wonder Solo Cornet except the valve slides which are made shorter so that the cornet will be in tune with itself when the "C" attachment is used. When the cornet is used in Bb and A the Vocal attachment is removed and the tuning slide inserted in its place.
Instructions for the use of the Wonder Solo Cornet with the Vocal attachment:
To use the cornet in "C" remove the tuning slide and insert in its place the "C" attachment, shove up the valve slides and use the Bb shank in the attachment. To use the cornet in Bb and A, replace the tuning slide and draw the valve slides to the mark indicated. Each instrument is furnished with two mouthpieces, music-holder, piston wiper and water key. Cornets are complete in handsome velvet and satin-trimmed cases, and are furnished with the Hoch patent bell mute, and are sent for six days' trial and approval.