This isn't an "obvious" clerical mistake though. It's common for option schedules to be unique. I could absolutely see a person whose work is supposed to go on for about a year being given a schedule commensurate with that timeline.
As for sitting on it for 30 years. Lawyers are expensive - more than the cost to resolve the issue 30 years ago, but given the recent stock climb, it's now more than worth it.
I would have sued.