Here is some exciting news! I have just purchased an Edwards T350-E trombone! It is very similar to the one I have been renting from the university, but quite a bit older if I am reading the serial number correctly. 

It is a 321CF yellow brass bell, Thayer axial flow valve, yellow brass single radius tuning slide, and a T-STDN standard slide (as far as I can tell…the older slide is marked differently than they currently mark them).