The Conn and the Holton both have bell keys on opposite sides, and this is a function of when they were built and a feature common to most of the early saxes I have seen whether these were tenor, C-melody or alto. I haven't been making a careful study of it, but this appears to be the case regardless of who made them.
The easiest way to tell a C-melody from a tenor in a photo is that the bell is narrower on a C melody and it sort of has a "slim" look to it compared to the alto and tenor models. There are also fatter C-tenor models (rare) that were built for orchestra use, but I don't think many orchestras really used them. I've only seen those in photos so far. It seems redundant for there to be both C-tenors and C-melodies, but at the time the C-melody was built when (before amplification was common) saxophones of full dimension were very loud compared to other instruments. The C-melody is slimmer because they wanted to "tone it down" for use in chamber music with instruments that could not be as loud.
So now all these sax players experimenting with resurrecting C-melody instruments are expecting the projection they get from altos and tenors. Mostly the Cs get upgraded resonator (hard) pads with metal domes or resonator pads. I think it makes the instruments tonally uneven. The original pads for these were soft as pillows. I salvaged a handful of the original pads off the Holton and one of the better USA pad makers will make me an original type set if I send them an example pad to copy. I thought that was pretty bonus to find a company that will do that for a reasonable price. So that's the goal for my jigsaw puzzle Holton C-melody. It's destined for the way-back machine restoration route, which should give me a very mellow less aggressive saxophone in C. For my current performance situations, that will be a big plus. I never realized how loud saxophones can be until I played one. These truly do not need amplification at all.
