The pictured horn in the OP's post is exactly what I marched with in the Cal Band from '71 - '73. Great sounding horn and beautifully made with satin silver and gold wash bell. I think the horn I used was "thrown in" to the deal when the Cal Band purchased a full set of eight (or maybe 10) BBb Sousaphones in frosted silver with gold wash bells. The Besson USA guys were trying to get the band to purchase matching euphs. Tough as nails with heavy brass, and damned awkward to march with. The bell points in when you are at parade rest. You have to flip the horn around your body to bring it to playing position, and most of the weight rests on your thumb with just a thumb hook, no ring or cross bar.
Doug
Adams E3 0.60 Sterling bell - Prototype top sprung valves
Concord Band
Winchendon Winds
Townsend Military Band