The key is to avoid Sovereigns built 1993 onwards. That's when the GS abomination was launched. I've owned one and played two others and they were all dreadful. The physical identifiers are short main tuning slide, large buttons, but a choice of milled or smooth, unsoldered lead pipe (but with no stay midway between mouthpiece receiver and 1st valve casing), 3rd slide water key on a full length 3rd slide, and comically thin metal, ostensibly for resonance purposes (according to the blurb of the time) but in reality for cost reasons. These should be cheaper than the model immediately preceding them because they're not s good, and the discounts available were enormous.