From time to time, I've been fortunate to acquire Saving Banks and Cards. The most recent was a Savings Bank. It is a metal bank disguised as a book about the size of a palm. The bank would own the key and they were issued to customers to assist in saving pocket change. When the customer was ready to deposit they would bring the book bank in to the bank and deposit the coins. It was partially filled with mercs and wheats. I paid $5 for the bank at an estate sale.
The other savings cards I received from my pick-up bank. To encourage savings, banks would issue cards with slots for dimes. When the card was filled, the customer would deposit the card. I have 4 full cards of mercs. I kept them in the original cards.