Just for future reference, Ed, the term used for these later metal core chips is bi-metal core. They don't use brass for the cast slug as the earlier Nevada chips did, but use a lighter bimetallic alloy.

I could be mistaken, but I think the Hyatt Lake Tahoe brass-cores were the last to be made with the heavy brass slugs. Even there, the reorder of purple $2.50's for Hyatt was a bimetal chip, not brass; they are lighter than the originals although they were able to match every other paremeter almost exactly.