The C-melody horn was what they called a "parlor" horn. Before there was TV, radio, or even phonograph players, members of the family would gather in the conservatory and play sheet music. By putting a horn in C, the player could read off the piano score. Once all these newfangled gizmos came out, "music night" became a thing of the past, as did the demand for the C horns (most manufacturers also made a C-soprano).
C-melody horns were generally not pleasant sounding horns compared to the more standard Bb and Eb horns. The later Conn C melody horns were generally considered the best of the bunch. They are still fairly plentiful on eBay, although they are generally overpriced.
I owned a '26 Buescher True Tone C-melody for a while, but eventually sold it, simply because I really didn't have a use for it. I hated the True Tone's double pearl octave key and thumbrest, it used to pinch my fingers. I prefer the '30s and 40's Aristocrats through the Model 156. IMHO, the Buescher Aristocrat is probably the best bang for your buck in the vintage horn market. Most collectors and players want the Buescher 400, for good reason, too. The Aristocrat was considered a "classical horn" a la Siguard Rascher. The exacting nature of classical music meant that these horns had to be set up well in terms of intonation and if you set them up right, they make great jazz and rock horns.
Bueschers generally fetch less money than comparable Conns of the same time period. Even though they cost less, they are not the lesser horn.