You won't be able to date the horn via the serial number because it is a Conn stencil horn (that is, it was made by one instrument manufacturer for another company to put their name (or stencil) on to sell as their own line). The serial numbers on Conn's Stencil horn contracts don't run concurrent with known, published serial number lists of their regular, Conn line of horns. The separate records for these are missing/destroyed, making positive dating via the serial numbers impossible. I have a few Wurlitzer stenciled Conn horns, and they are usually much nicer than many stencil horns, with full engraving, Silver plate, full key work, heavy walled bodies etc. The only thing they lack are the rolled tone holes of the fronline Conn horns, typical of Conn stencils in general..

Right you are Charles, and the Martin C-Melodies were some of the best. In fact, there are three main camps currently that will avow that their choice for the best make/model of C-Melody is the best intonation/ergonomics/tone wise: Conn, Martin, And Buescher.