Pinpoint Ph probe ?
 

I bought a used Ca reactor awhile back and it came with a Pinpoint Ph controller which had a couple of probes with it. One was sealed on the tip with storage fluid and the other was left exposed/open. Will the exposed one be usable/accurate or should I just toss it ?

It's accurate as long as you can calibrate it with the ph solutions. Keep the probe in your tank for a day or so before calibrating.

Usually a bad probe will jump around in the values it displays or take a long time to respond to changes in PH.