"I'm not real sure how to "test" them though-- other than
put 'em on the Sencore and see if they really do trigger at the rated
voltage"
I assume they act like varistors.. You could put them on a curve
tracer, too.
If you feel really gutsy, drive the WG from a function generator
and increase the slew rate while watching the high side of the
deflection yoke and see if you see it 'ring' at all
