Frankly, it doesn't sound as if the Master Cornet is being held for investment purposes, and shouldn't. There are beat up models of it from all years that come through ebay. The valves are quite standard on those horns, especially if you get the same year range. It would cost you a great deal less to buy a horn for the valves and keep the old ones if you wish. as an aside, I have a few Masters as I find them fabulous cornets (prefer all brass too)..and none of them have what appears to be ANY wear on the valves. In fact they appear to be all nickel if not nickel with a nickel plate.. Mirrors all.