PD schematic interpretations

[Max]

please write here your interpretations of PD schematic

my interpretation is that is made basically of 3 different circuits:

1. Heathkit GD348 MD with omega+round smaller coil, working as usual old IB VLF MD with unshielded coils and at same expected range of an IB VLF MD with that small coils

2. passive receiver circuit made around a couple of ferrite rods antenna (directive) and tuned in LF band (long waves) maybe around 60Khz, to receive some very strong LF signal like time radio station WWVB of NIST and the like

3. mixer and monostable circuit that mix output of the MD and passive receiver and then feed a 555 that controls buzzer for audible signal and led

I don't see anything else interesting

please provide your interpretation too, expecially Geo

regards
Max