Jan,
The WA52-2 is the original mouthpiece shipped with the Besson Prestige when it was reintroduced by Buffet-Crampon. I think that Wick's production (or at least their sponsorship of Steven) got messed up when the Besson part of Music Group went into receivership. So when the new Prestige first came out, Steven was pushing the Alliance mouthpiece. The choices were Alliance E2, E3, or E4, equivalent to SM3, SM4, or SM5 respectively. The model numbers you see now (WA52-2, WA52-E, etc.) are a new system. Within about a year or two, Steve went back to Wick with the SM3U and later SM3X. If you look at the new SM3's, they look and play a lot like the Alliance. Steve no longer promotes Alliance AFAIK.
I still have my Alliance E3 (WA52-3?). After my Wick 4AL, it is the only other mouthpiece I use on euphonium.
Adams E3 0.60 Sterling bell - Prototype top sprung valves
Concord Band
Winchendon Winds
Townsend Military Band