Listed only by Irwin, who says: A Foundation stop of 2' manual and 4' pedal pitch. It has much of the Gemshorn's transparent and clean tone, but the overtones at this pitch are harder to hear, making this tone color less apparent. This fourth harmonic of the Gemshorn Chorus is useful with or without the other Gemshorn ranks. It may be on the Choir. It is never shrill or fluty in tone, but clear and neutral-colored, in spite of its pitch. It is useful with the stops of the String Organ, since a 2' String is quite a bright timbre. It is not a substitute, however, for the regular Great Fifteenth. Its spotted metal pipes are of very small scale.
Only one example of Gemshorn Fifteenth is known, and none of Gemshorn Super Octave or Klein Octavengemshorn. Contributions welcome.