I share a few pictures of my Conn bass trombones: 70h (1952), 72h (1963), 62h (1970), 73h (1977) and 71h (1979). I shared pictures with the help of "imageshare" You upload an image on their server and then copy and paste the URL.
This is the 72h on the left and the 70h on the right.
Both have the same bell profile and they need the smaller cup. They have not the exact valve design and the braces are little different.
The 72h feels a bit larger compared to the 70h The 70h has a bit more "snappy" attacks and brightens up if played very loud. It has another spectra of sound with more colors. I'm thinking it must be the TIS. Both has the B when I pull the f-slide.
Here is the 72h (to the left) next to a 71h
I tested both with the f-valve slide pulled as far as possible and on both the B is possible. Both must have longer slides compared to modern basses.
I removed the f-tuningslides and compared them. The one on the Conn 72h is longer which means it can be pulled a few centimeters more compared to the 71h, but the maximum total length of both valves seems to be equal when I measure with a string. There is a difference in disposition of what is movable and what is not, but I'm not sure which is best and how this can work.
When I play both horns the 71h seems more thight compared to the 72h which is more open. I wonder what else is different? What about lead pipes? The 72h is an Elkhart from -63 and the 71h is an Abilene from -79.
From the pictures you can se there are differences in the tuningslide and valve section where the 71h misses three braces.
I'm thinking the reason to build the 71h like this is it then shares the first valve design with the 73h. Maybe it was cheaper to have one valve design for the first valve. A design that works also when they add the next valve to build a 73h. You can see that on the next picture. The 72h and 71h plays different, but is it possible that might not have been their primary intention but a side effect?
Here is the 73h to the left and the 62h to the right.
The 73h bell is the same as the 70h, 71h and 72h.
The bell on the 62h has another profile. It needs the larger cup, the cup that fit most modern basses.
The slide is the same length on 71h, 72h and 73h.
The 70h has a 2 cm longer slide compared to the 71h, 72h and 73h and of course can be extended since it has tuning in the slide. The 62h has a slide that is 4 cm shorter than the non TIS slides but can also be extended like the 70h since it has tuning in slide.
As you can see both the 73h and 62h has almost the same valve design or it's the longer goose neck on the 62h that makes them look a little different.
Both these horns came with the second valve in E. The 73h now has the "Stauffer D-slide" that is no longer made. I had Lars Gerdt (builds trumpets) in Stockholm to build me a copy of that "Stauffer D-slide" to fit the 62h.
When played the 73h feels smaller compared to the 62h.
The 62h is the only one that is red brass. The others are all yellow brass.
I played the same song on all five of them. The 71h and 73h definitely are more "tenorish". The sound of the 70h is very colourful. The 72h feels a bit larger compared to the 70h but I don't think it is. I don't know about any differences in lead pipes? I consider the 62h to have the broadest sound and is definitely largest sounding bass in the herd. All these horns are a joy to play.
/Tom
Is that a Conn 70h "Fuchs" model? 
I might pull the leadpipe, but haven't decided on that yet.
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