I've been playing bass trombone seriously for about 4 years.  In my previous playing, I always played first or second parts, but I had instruction back in college with Robert Raddock, who later became Director of Bands at Disneyworld.  

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I bought a used Conn 110H single-rotor bass in 2019.

https://www.conn-selmer.com/en-us/instruments/band-instruments/trombones/110h

 

Up to that point I was playing a Conn 88H symphonic bore tenor trombone.   In November 2021, I bought an imported double-rotor bass from Dillon Music in New Jersey.  
 

https://www.dillonmusic.com/dillon-bass-trombone/