To be quite honest, there is an anonymous instrument, documented in the beautiful catalogue by Günter Dullat on the 2014 exhibition on saxophones in the Markneukirchen museum, which is probably built by V. Kohlert in Graslitz in the mid-20s, or, even more likely, by F.X. Hüller. It is called a «¼–tone–saxophone», an alto in Eb, with a lot of extra keys on it, whose functions are not immediately clear from the picture. It is not even clear whether or not the instrument in question is indeed the ¼–tone saxophone. The text states that only two of these instruments are presently known. The instrument goes down to a written low-A. There is no account of its acoustical behaviour.
The instrument was possibly made on the instigation of the composer Haba, who was a professor at the Prague conservatory and at that time (1920s) was experimenting with quarter tone music. In 1943 Haba published music for quarter tone clarinet, trumpet and trombone. However, no mention of a quarter tone saxophone was made in this piece.