Here is a nice Vintage Conn 4D single F Horn.  The serial number 313828 would date this one to 1936, the first year this model was made.  There was a 4D in the earlier 30s but it was laid out like what became the Pan American.  The bell inscription reads:  C.G. Conn LTD, Elkhart, IND, USA.It's in remarkable condition for its age.  There are some signs that dents have been repaired along the bottom of the bell and at the edge of the flare.  There are only a few minor dents that remain.  The valves are smooth and fast and they still have good compression.  All the slides pull easily.This horn has the beautiful squared off bracing that was used on the Schmidt model 6D and the earliest all-rotor 6D.  This is the only one like this that I've ever seen and I'm old.  I have one from 1937 that doesn't have them, it has the common ones that they used up until current times.  It has the original case that shows some age but is in solid condition.  It has the Eb crook, the cleaning rod and brush and the care booklet that has the warranty on the back page that shows the serial number of this horn and is signed off by the Conn inspector.