How do you do that?????

I am ready to clean up the dist. that was in my donor engine. The only book I have for the year of the engine is a med. size Hayes. It shows that there is a retaining ring at the top of the shaft. This is inside the well you see when you remove the rotor. I think I can see the retaining ring but HOW do you remove it?
Tag on the dist. has these numbers on it:

27 6
3874115
Thanks,
Mike