AETHERPHON, global theremin family

> You can use a small, jeweler's screwdriver however -- if you force the
> coil adjustment too far it is easily damaged.  The plastic tool
> reduces the risk of damage from over-tightening.

That's not quite right.

The damage comes from the screwdriver being a hard wedge, and the core
being VERY brittle ferrite.
Pushing the screwdriver in hard enough to make it turn the core, puts
enough pressure on it to crack the ferrite if the screwdriver isn't
held exactly vertical.
Radio shack sold a kit of tuning wands, which work nicely. I'm not
sure if they still sell them.

Also, the metal of the screwdriver will affect the tuning.

It seems like sacrilege, but I've been very tempted to drill a small
hole in the upper case, right over the coil, so I can tune without
having to guesstimate the shift of installing the upper case.