Mentioned only by Audsley in his entry for Corno di Bassetto, who says:

According to Hopkins, a stop labeled Corno Bassetto, Soprano, 32 ft., was to be found in the Organ in the Cathedral of Como, but regarding the form of this stop we have been unable to obtain information.

Audsley did not see fit to provide a bibliography, but he may have been referring to the Hopkins & Rimbault[1] in ours.

Bibliography