Date: 1928. Owner unknown
According to research, Conn introduced the F Mezzo Soprano in the Spring 1928 issue of its Musical Truth magazine. The 22M F-Mezzo as well as the 24M Conn-o-sax were attempts to squeeze some more life out of the saxophone craze of the 1920's, which by 1927 apparently was dimimishing rapidly. Very few of these were sold, and apparently many 22M's were intentionally damaged to serve as practice material for instrument repair students. More info can be found here: The Saga of the F Alto Saxophone".
What Conn said:
Here it is, a wonderful new saxophone, new in voice, new in tone quality, new in size, new in scale and new in playing possibilities, the marvelous new Mezzo-Soprano Saxophone in F. Recognized by artists as the real solo voice of the saxophone family.
Only Conn's resources could develop such a saxophone. Only Conn coud build it. Since it's introduction, the Mexxo-Soprano in F has won a commanding position in the music world. It opens up a whole world of music never before available for saxophone players.