A full, not compensating, double.
It requires no compromise of intonation on valve combination, as is the case with compensating designs. The fifth valve is a Bb-F rotor. The fourth valve is a muting valve that lowers the horn 3/4 step to bring stopped horn mutes into tune without intonation. Extra fourth slide puts Bb in the key of A, so written E horn parts do not have to be transposed.
Key of Bb/high F Descant. .468" bore; 12.25" large-throated, hand-hammered, yellow brass detachable bell; 5 valves; tapered, hand-lapped brass rotors; brass branches and crooks with solid nickel silver connecting ferrules; slides are hand-lapped brass both inside and outside; lacquered brass finish.