An original rotor on the right with no rivet, and an aftermarket on the left with round-headed rivet. Note that the rotor on the left is from an aftermarket electronic ignition system and has an extended base containing magnets to trigger a Hall-effect device.

Showing the rivet inside the circle of the base i.e. too close to the distributor shaft and hence prone to breaking down.

Another style of currently available rotor. Still with the round-headed rivet but fitted outside the circle of the base i.e. further away from the distributor shaft and so probably 'safe'.