One good used  switch

 

BNC jacks look to be silver plated

  Sorry I have no specs on this.

Came from 1960s Jerrold FD 30 test equipment that was in excellent condition and looked to have had little prior use.

See picture describing from FD 30 ad regarding the mercurywetted switch

We do not know what it needs for voltage or frequency to make it switch back and forth. The coil looks to be many turns of fine wire and measured 9.7kohm on our fluke digital multi-meter.

the switching capsule inside the coil is a sealed glass bodied assembly

This does not appear to be a simple A/B switch but looks to be a high speed alternating type?  A continuity tester on BNC center pin shows continuity to all BNC jacks,  so assume it needs some type of pulsed or AC signal on the coil to make it oscillate between the two.  Once again just a guess on my part. I could not find schematics for FD-30

4x2.5x1.25 inches

9.1 oz