Old trumpet question

[ThomasDodd]

This is for the old timers and historians here.

A guy in the community has an old trumpet. Supposed to be from the 40's. I think teh name was Martin.

It's interesting in that it has 2 sets of valve slides and a second, clamp on, lead pipe. It appears to change the open bugle to C.The extra lead pime drops down earlyl, and mthen the new tuning slide is long and narrow, kind of like the 3rd valve slide.
Ring any bells?

He's wantuing to know more about it and it's value. It looked pretty good and was in the original case, designed tio hold the extra slides.

Only issue is it seams to be really flat. The reciever is a little small for modern mouthpeices. He's got the shorter valve slides in an attempt to tune it.