> looks like a different version

These were late-90's=20

> Ceramic pieces were there too

Now that I think of it, those ceramic blocks must be reactive at
RF frequencies. They are attached to the copper box by the brass
nut and bolt but are not in contact with the moveable copper disc.
Its proximity to the ceramics and whatever they're doped with is
what tunes the unit

But we digress ....

Joe
--=20
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