This information was taken from the New Grove Dictionary of Musical Instruments:
“OCTAVIN (Ger: Oktavin). A single-reed woodwind instrument, conical in bore. Its invention is usually attributed to Julius Jehring (1824 – 1905), a bassoon maker; in fact, Oskar Adler, a maker in Markneukirchen and Hermann Jordan of the same town were granted the German patents (on 27 September and 11 October, 1893) and a British patent (31 October 1893). The instrument, 40 cm. High, is made of rosewood (palisander), resembling the butt-joint of a bassoon. To the wider bore is fitted a small metal bell, turned outwards at a right-angle; to the narrower, an ebonite joint is added, terminating in a clarinet-type beak mouthpiece. 14 keys and three rings are fingered, much as a simple-system oboe. It was originally made in C and Bb with the compass from a to f’’’ (or g to eb’’’); there is also a straight single tube model, and a bass,descending to G, is mentioned by W. Altenburg (Die Klarinette, 1904). The octavin, which attained no popularity, has a tone somewhat like that of a soprano saxophone but less pleasant….”