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This is a traditional wrap Bach bass trombone with a dependent secondary valve. Even though it was made recently, it was ordered by a percussionist band director who didn't understand about linkage, and it originally had the super old-school linkage (whereby the player slides their thumb over to play one valve or both valves. At the request of the college's recently promoted-to-chairman faculty member who is also the trombone studio teacher, I split the linkage up, but I didn't buy anything to do it; I recycled nearly everything that was there, and also scrounged some old 1960s linkage from a chrome plated Olds marching key of GG contra, which featured one piston and one rotor, so this instrument remains all-American.
I think the rollers actually define this linkage as feeling nicer than without them, as they allow the thumb and middle finger to glide across the levers just a bit.
Anyway... This defines the tail end of repairing those six instruments that this chairman/studio teacher handed to me to repair and (in the case of this one) alter.
now, for the only rewarding part of this multifaceted project:


(Who cares about the quality of my work...
I only try to do nice work for two reasons:
- self amusement
- to avoid being hollered at )

(They asked to consult me on Artemis II, but I told 'em that I have too many trombones to fix.
25,000 mph re-entry speed...They should be able to figure that out without my help...or - just as freeing up the Strait of Hormus - leave it to the French.)

This was the configuration prior to the conversion:
Most everything you see after the conversion is recycled from this configuration except for a little bit of it:

Both valves were controlled by the left thumb, and you had to roll your thumb across from one paddle to the other.