It looks wrong to use a coil in this way as you’d expect a similar coil to form the inductive part of a tuned circuit, but this coil is shorted out to prevent its inductance becoming a factor ...

Just a signal generator making a 125 kHz square wave, coupled to a two transistor buffer pumping a tuned circuit. The tuned circuit is the coil scavenged from an old RFID card, and the capacitor ...