Trying to strip the factory finish off acorn style center caps? What works?

I've tried using EZ-Off and the coating on the center cap doesn't seem to be coming off with it, no matter how long I let it sit on there. The coating also seems impervious to glass bead blasting. Any other thoughts for removing this pesky old school coating/finish? I really want to avoid purchasing a new set of center caps for roughly $300...