My friend is going to be selling me his old martin Galaxy straight trombone, and I could not find any info whatsoever on the instrument no matter how hard I looked. I don't have the instrument at hand at the time of writing this but the serial number is somewhere near 720xxx. It seems to be a .500 bore with a yellow brass bell with a few scratches, the slide however is very rusted and loud. If anybody could find and give me info on this instrument it would really help, because the friend I'm buying it from doesn't know how much it's worth.

Galaxy was a Holton model. I believe it was the step-up above the Collegiate. You sure its Martin and not Holton?

Martin horns included an Indiana (student), Imperial (originally small tenor and later step-up), Dansant, and Committee (pro model replacing the Imperial).

.484 bore, made 1984-1986

Search the Net for Martin Galaxy TR5100 trombone.

I'd get a tech estimate on repairing that bad slide before buying. Repair might exceed the horn's value.