Deuteronomy 23:20 indicates that Jews were lending institutions. I hear it that Jews therefore kept vaults and were trusted with jewelry, ingots and other small valuables. Then that developed to transferring the valuables and so instead of withdrawing a few coins to buy something, and the seller would be depositing those coins into the same vault a note could be written - a bill of sale. The item would be sold and the ownership of the coins would transfer. Islam created the Sac, becoming a check. This is where transfer of the coins over a distance was unnecessary as long as there was an accounting and eventually (armored car) the vaults were balanced out.