It seems to me that the white Mefferts and Tomy Pyraminx are the same thing, and the best one's ever built. They are the ones with yellow stickers, the white pyraminx with gold stickers are poor knockoffs from my experience. The black pyraminx seem to pop alot.
you can get a sealed pyraminx from 1981 from mefferts for $18! that's a steal if you ask me.
http://sites.webec.com.hk/meffert/index ... product=15