Meinl Tuning Fork Sidereal Moon TTF-M-SI, Description: Duration of one orbital period around the earth, measured from a fixed-star-position; Orbital period in days: 27.321661; Orbital period in seconds: 2360591.51; Frequency calculation: 1/2360591.51 sec. = 0.00000042 Hz, (0.00000042 Hz x 2) 228 = 227.43 Hz; Frequency: 227.43 Hz (= 29. Octave); Tone: A3#, Shifted 440 Hz standard-pitch: A4/a' ? 429.33 Hz, Made in Germany