Difference between rev limiting and standard Rotor
 

The resistance on wires appears to be within spec. One a little low and one a little high. When checking resistance of the cap on an 81 SC O noticed that it spec'd as a rev limiting rotor per the Bentley manual. Is this rotor specific to a model and year or is it just an option.
Thanks Rob

If our car is a ROW car, then the rotor is all you have to protect you from over revving.
A US (and some other destinations) car/engine has an electronic rev limiting circuit in it.

They rarely work after all this time and are expensive.

I installed a RL rotor on mine.

So we can run either one?

yes

Thanks for the help!

Or you could skip it all together.
An SC have no problem going over the stock limiter, it's just mostly useless.
A limiter doesn't protect from the dangerous type if overrev, missed shift.

This.
And that's probably the most common type of overrev.

The main benefit of a rev limiter is in case the throttle gets stuck somehow. With steering column licks there is some risk in turning off the key at highway speeds, so putting the clutch in while braking will keep the engine from exceeding whatever the limit is until you feel safe turning the key off.

The mechanical limiters are pretty effective, and by bending the tab which holds the spring you can adjust where they cut the spark off.