How to remove old style chainring held in by a single nut between bearing and chainring?
No exposed threads to check.  The Sheldon Brown site was helpful in general, but couldn't answer the direction, but led me to find a Park Tool page which suggested it should be right handed.  That knowledge combined with the PB Blaster sitting on it for a couple hours and I was able to break it free with a few hard hits from my rubber mallet again.