The handrest changed with the introduction of the 967GS (full floating leadpipe) in the mid 90's. The Round stamps had the early handrest and the metal tab valve guides. Then Besson switched in the mid-later 80's to the later style plastic guides but the leadpipe was still soldered to the bell and it had the early style handrest. The German built horns are based on the 967GS design. One change that I do NOT like in the newest German sovereigns is that the 1st valve compensating loop no longer has a removable slide.
Other than what I have described, Barry summed it up quite nicely.
Adams E3 0.60 Sterling bell - Prototype top sprung valves
Concord Band
Winchendon Winds
Townsend Military Band