Timing tab confusion

Those were for a short-lived timing sensor- it would hook up to the old engine analyzers (there were hand held versions, too), there was a probe you'd slip into that tab along with all the other hookups and you could get timing and advance readings from your ignition system. Most manufacturers had them- I believe Chrysler started using them with the Lean Burn systems, and some of the pre-OBD TBI motors still had them.
Go ahead and toss it.