Shard Banking System

Currency
I want to have a currency system that involves different types of coins of different values. Gold, Silver, and Copper come to mind, but i am not sure how to distribute it. I know that WoW does this, but I'm not sure what the denominations are. Perhaps something like:
 * Copper = 1 "Currency Name"
 * Silver = 5 Copper
 * Gold = 10 Copper or 2 Silver

another option which would spread things out a bit more and make the currencies a bit more useful is:
 * Copper = 1 "Currency Name"
 * Silver = 20 or 50 Copper
 * Gold = 50 or 100 Copper

Banking System
When you "Bank," you will be given a menu of options which include:
 * Deposit - You may deposit checks or currency into any bank.
 * Withdraw - If you have deposited currency into a bank, you may withdraw that money from any bank. You do not have to return to the bank where you deposited it.
 * Write Check - This option allows a player to write a check to another player. The check can be for any amount up to the total amount of currency in that player's bank. The money is consumed and the check is placed in the player's pack. The check can only be accessed by either the player who wrote the check or the player to whome the check is written. Checks are "Blessed" items.
 * Safe Deposit Box - Players my deposit and withdraw items from banks aswell. However, any item other than currency must be deposited into the player's Safe Deposit Box and can only be withdrawn from the bank where it was deposited.