Vintage Helleberg question

[MartyNeilan]

this is probably a dumb question... but just eye balling the insides, i've wondered if the conn sousaphone mouthpieces like i played in high school were the same as the helleberg's but heavier walls and rims?

Conn2=Helleberg 7b (rim may be different)

[iiipopes]

this is probably a dumb question... but just eye balling the insides, i've wondered if the conn sousaphone mouthpieces like i played in high school were the same as the helleberg's but heavier walls and rims?

Conn2=Helleberg 7b (rim may be different)

I have owned a Conn 2. It is deeper than a 7B.

[Donn]

I find the Conn 2 and 7B to be 1.42" in depth. No difference, to the best of my ability to assign a bottom. The 7B appeared to have a very slightly narrower throat, but not within my ability to measure. I measured to top, not to rim bite, so you could take a very small amount off the Conn 2 to account for the extra rim height, but I don't think these measurements are sufficiently precise to warrant that. I put the back end of a drill bit up the bore until it felt like the bottom of the cup, and then put the caliper slide against that and ran it out until the base of the caliper appeared to be in line with the top of the mouthpiece, just squinting at it. I think that's good to 0.01", but certainly not much more.

Conn 1 is 1.72" deep, and Conn 3 1.26", per same measurement.