Ken posted:

I've acquired a couple of probes marked "PR 200" & "PhilipsECG" on one side
of small box integrated with connector, 1/1-1/10 with adjustment hole on
other side (calibration?). Three-position switch on probe marked 1 - 10 - G.
I assume this is 1x/10x multiplier/ground selector.

I agree; it sounds like scope probes. The adjustment compensates for the coax
attenuation. When using a scope clip the probe to the "calibrate" test pin and
observe the scope display. Rotate the variable capacitor via the adjustment
hole to display the best squarewave.

Don