I think it was for a marching tuba. I pulled a couple pads out & it works well for many front action tubas. It fits the parts tuba I have for sale, and I'm pretty sure it fits a York 712 just about perfectly, and *probably* a 716 with an upright bell. The York Master is just a tad too wide through the body. It probably fits a 2341 new style & similar, but a pad seems to put some pressure on the bell by design.
The pad at the bottom bow is quite large and could be modified/replaced for a very tall tuba or to improve the fit. I still have the pads.
Photo with the parts/fixer that looks like the Cerveny/Amati 686
