I know a bit about Trombones as I normally play Bass Trombone. It is a medium bore Bb Tenor Trombone with 'King 2103 USA 3B' written on the bell and the name 'King' written on both sides of the circular balance weight in gold writing surrounded by black. It has numbers '39' a small gap then '270488' stamped on the instrument by the screw thread near the lead pipe and '5308' stamped on the slide part. It is Brass lacquered and the lacquer has worn off at the parts where you position your hands otherwise has no obvious damage and the slide is very smooth to play with no dents. It has a Besson '7' mouthpiece and a very old style unmarked mouthpiece in the case with it. The case is Hard, black leatherette, has a 'King UMI' label stuck on it and is locked by three fasteners but has no key to lock it. Inside is bluish velvet and has a small storage compartment for the mouthpieces. I've cleaned it up like my current Bass Trombone as it hasn't been played for a long time. It has lovely tone to it when played. I was left this in a will as I'm the only Brass player in my Family and am thinking of selling it as it's a bit small for me. I've looked at some King 3B sites to see how old it is but none give any details about an 8 figure number, a 2+6 number or a 4 figure number for the slide. I've seen some on 'E-Bay' but they look a lot newer than the version I have. Any replies would be most welcome as I wouldn't like to put this into storage when it could be put into good use.