Very good, you nailed it. I guess the coil taps, and variable cap pointed to the tuner.
Both circuits very simular and do the same job, frequency resonance.
Cyrstal rigs are still around, and have gotten sophisticated if you want them to be. I have been playing around with them a bit.
Take a look at MidnightScience
. They also have a rather lively discussion forum Rap 'n Tap Discussion Group
that is just as friendly as this one.