Old horns can be really cool. Take a vintage Besson Meha Large Bore. If is in mint condition, what a wonderful axe! One of my favorite cornets is my old Conn Victor. I used it at work last night on a trad jazz gig in Evanston.
The possible problem, as I see it, is the history of the horn. Was it abused? Are the valves worn out and pitted from poor care? Are the slides free? Etc.
I love my Stage 1 California model, and I wouldn't trade it for anything, but one of those Mehas would be pretty cool in my collection. I'm on a short financial leash, right now, however!
Nick