Another rarity is the 20 hole Knittlinger octave tuned harmonica. Just two models, the Marine Band Octave and the Auto Valve Harp are manufactured worldwide. The Auto Valve Harp, as its name suggests is a fully valved instrument, this makes it considerably louder than the Marine Band Octave but eliminates the potential for note bending. Reeds: 40 ; Reed plates: Brass 0,9 mm ; Comb: Wood.