A wood block 10.5 inches by 3 1/2 by one inch looking like a section of a reed organ chest. It has 17 slots with 17 reeds marked in order from left to right on a paper strip glued on, "Smooth third, tempered third, F,F#,G,G#,A,A#,B,C,C#,D,D#,E,F. You can see a picture at www.pnotec.com/pictures.html
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