some things went from patent to brev others switched to patent (e.g. center bolt on brakes went from brev. camp to pantent)... I think the switch from chain rings that say patent to those that say brev happened in the late 70s, maybe 78/79.

Unless the seller was advertising this ring as an older ring or specifically mentioned it to be pre CPSC I don't think they have any obligation to refund your money. I say hang onto it or resell it.

As for the cranks changing, well I don't know for certain, some people have pointed out the the bulge seems to be larger on post post CPSC cranks. The BB are definitely different though.