I just had to dig out my Conn 77A. Sorry no picture. It is a standard configuration for a cornet. The 76A, which replaced the 77A is quite a different design. The tuning slide, I'm guessing, is on the bell tubing? Anybody know of any other Conn cornet with that feature?
There are many many examples of tuning at the bell tail from Pan-American to Puje, including all of the opera-glass tuning Conns (That front slide is for quick change only on those, not tuning). This Martin Imperial is another and even manages to still keep it on the right hand side of the horn rather than the left hand most think of as the back.
Oh my oh my. Gotta start looking for one of those. Yowza!