I compared my Holton Clarke to the image Albert posted. No doubt at all ! What can we deduce from this ? The Holton-Clarke was first seen in May 1928 and Bix was playing it in Sept 1928. This does not mean that he played it exclusively for 4 months, but that he obviously did play it from time to time; and I think we can at last discount the theory posed by Ralph Norton (in the Evans and Evans book)that it was doubtful whether Bix favoured it very much compared to the "superior" Vincent Bach or Conn Victor Cornets.
I am going to start playing mine on a few gigs to see how it goes.The bore size is larger than the large bore Bach but smaller than the Conn Victor. We seem to deduce that he favoured larger bore instruments (as opposed to Louis Armstrong who favoured smaller bore instruments!)