It is a Bach Model 30 trombone, in the Bronx, serial # Dates it to late 40s but dad said it was sold 1950s...apparently only 1-2 were ever made...seems like custom specs.
Old Bach Gold Brass bell which is a little bit bigger than 8 inches and has a different flare design than a 36...Best Brass Tenor Practice mute will not fit...maybe a 50 flare that was cut off smaller?
Slide has gold brass tubes and is dual Bore medium...514/.525...a