Tuning fork clock

Custom designed and built clock using an 80 Hz tuning fork as an oscillator. Very few clock like this were built (though somehow more popular was a vibrating reed mechanism). The fork oscillations are maintained by an electromagnet, opposite side electromagnet acts as sensor driving a transistor base (the whole circuit consists of a NPN transistor, a resistor and capacitor). The clock works on one AA battery and consumes very little power. Fine fork frequency adjustment is by the two brass nuts on top of the fork, rising the nuts by one turn reduces the frequency to slow down the clock by 10 seconds a day. There are small, insignificant discrepancies between the model and the finished clock