I have one 314A that needs tested anyway. The pinout is the same as the 255A. I measured 143 ohms on each winding.

Testing the contacts is a blind test since they are sealed in a capsule. It also must be done with the relay in a  vertical position so the pool of mercury is not shorting the contacts This is true of any mercury relay. They can normally be tilted something like 30 degrees and still work.

UNDER NO CONDITONS TRY TO OPEN A MERCURY RELAY!!!  The capsule is under high pressure and mercury is not a healthful metal.

I used clip leads to make my connections, then stood the relay up The 1.5V battery test worked well. This relay is indeed bistable. When I put the ohmmeter on the open contact One battery polarity of the battery would close it. It would then stay closed after removing the battery. I moved the ohmmeter to the other contact, reversed the battery and that one closed and stayed closed even after removing the battery.

I would say I have a good relay.

Tom  N3CRK