Thanks Tom and Mark for the replies. I'll check for additional set screws
and clips. I really don't think that there is a set screw, but the clip is
a possibility.

I'm still puzzled by the wiring, since I can't see where the black wire was
ever connected to.
I'll keep digging. I'll have a volt meter with me next time.

Thanks again for the replies. Somehow I knew that Tom would be one of the
first to reply. You're always there with some quick friendly advice.
Thanks!

Gary