The Couesnon Monopole (Series I & II)
Series I
1937 - 1949 (#1 to approx #82xx)
Again, after Couesnon was reformed in 1931, there was a slight gap in sax manufacture (it may be that I just haven't seen any horns from about 1931 to 1940). After this gap, these art deco horns appeared. Bevelled tone holes gave way to rolled tone holes. Left hand bell keys became right hand bell keys. Double-socket necks are also introduced.
Note that these horns have a bit different serial number structure. It's probable that either when Couesnon was incorporated or when they moved to their new facility that their serial numbers restarted at 1.
The construction of these saxophones parallels only one other French manufacturer: SML.
Series II
1950 - 1980(?)
This series is marked by slight keywork design changes and different engraving.
There is no serial number chart extant for Couesnon. I do, however, find it difficult to believe that they produced saxophones after 1980, as their construction is far inferior to the Buffet SuperDynaction "transitional" models or S1, the Dolnet M70 or the Selmer Mark VII/S80.
However, I put their production end date so late because of Couesnon's 1976 saxophone neck patent (FR2277393), which is demonstrated on a Monopole neck.