Both the Monopole (model 140) and Monopole Conservatoire (model 141) show up by the 1934 catalog.
A few of these will have a star on the bottom of the bell engraving. The next ones say 'Monopole Conservatoire' with #12615 said to be from 1949 and #24818 to be from 1955. Some serial numbers go up to the 30000 range. I would ignore the serial number at this stage and go by the two-digit date inside the bomb for the date. These all have extensive bell engravings that include the name 'Couesnon & Cie'. The early ones are found in the 19 catalogs found on this site and the top models are the Monopole. After buying a Couesnon Monopole Star flugelhorn recently, I looked up every flugelhorn I could find on the internet and in catalogs to see what I could find out about serial numbers and dating.
