Question I have, what seem to be, a 1923 F.E. Olds trombone serial number 4249. The unusual part is tuner "threaded rod and locking wheel".
Have not seen this feature before. Have you? What is it?
Answer If I understand correctly, I believe that you are describing an in-slide tuning mechanism. The rod and locking wheel were to hold the horn at the desired pitch. The slide is made up of the typical inner and outer slides. But in addition, there is a third section of tubing that will shorten and lengthen the outer slide. Olds used this configuration in its standard model at that time. They moved the tuning to the bell section in their "self-balancing" model.
Please note: My area is BRASS instruments, not other wind, string or percussion instruments.
I will provide information on antique, obscure and out of production BRASS instruments.
1) Please don't ask for evaluations, I'll not provide them on this site.
2) I am often asked very similar questions, so I'd invite you to first check on Horn-u-Copia.net. Much of the information I have garnered about this topic, I have posted on this WEB site.
I perform in several historical bands, have informally researched the area, repair brass instruments, and operate a Forum dedicated to the topic at http://horn-u-copia.net