Value parameters

1- Denomination
2- Rarity
3- Metal scrap value
4- BTC scrap value
5- Utility , as a hardware wallet

New versions will lose simple denomination, but the hardware wallet value could be enhanced.
 
a) Durability, I see other products able to survive high temperatures with codes built into the metal.
b) A public address QR code to make balance checking easy.
c) A signed QR code balance sticker generated by Casascius, to place on the new coins later.