Want to use 4 ores for coins: copper, silver, gold, platinum. Each one has a value 10 X more than the previous.
1 Copper = 1
1 Silver = 10
1 Gold = 100
1 Platinum = 1000
The ore is also 10 X more rare as you go up in value. With copper having 1000 spots per sector and platinum has 1 spot.
These ore would not be used for pure armor but could be used for gilding or something: Silvered Iron Plate Chest Armor.
Maybe it would give magic or some other resistence.
They would for sure all be used in jewelry making: crucibles and molds, etc. Maybe each metal gives +2 or +5 per level.
Probably use CP for CoPper or Copper Pieces.