Listed only by Irwin, who says: A Diapason or Principal of 5-1/3' on the manuals, and 10-2/3' on the pedals, belonging to the sub-unison series of stop-pitches. It is formed from open metal or wood pipes varying in loudness according to the 16' manual and 32' pedal stops it is meant to augment. It sounds the important third harmonic of this series on manuals and pedals, and speaks at the fifth above the key depressed. In practice, the name Quint usually implies a Diapason, and the name Quint Diapason is almost never used.
Quint Diapason 5-1/3', Solo; John Wanamaker Store, Philadelphia, Pennsylvania, USA.