Before Shimano with there Bio-Pace chainrings, we had . . . P O W E R C A M !
Yep . . . that's a 60 tooth chainring folks.
The concept is simple . . . the design, not so much. The concept is to advance the chainring during the bottom of the down stroke when your leg strength is at it's peak. Then during the up stroke the chainring retards to it's original position. Yes "advancing" and "retarding" are industry terms. Check the Science
I traded something for it a long time ago. It works fine when you have chain tension. When you don't it tends to clang a bit if you don't watch it. It was desinged for time trials more than anything. It was heavy, and I didn't see any pros like Greg leMond, Bernard Hinault, or even Francesco Moser using one, so it sits in an old cardboard box since.
Heck it might have worked, who knows, I'd never know, I followed the sheep rather than do some practice TTs on it and seen for myself. Hmmmmmmmm . . . I smell experiment . . . don't you?