An Update:
For the early cars there were two types of ignition rotors available, one with a rev limiter, and one without. The rev limiter protects your engine from overzealous drivers. A small floating weight on the rotor grounds out the coil at the RPM limit preventing valve train and other engine damage. In 1978 and later, rev-limiting is controlled by the CD-box.
http://www.pelicanparts.com/catalog/...BAStun_pg1.htm