Debit cards are like cash, direct link to your account. Credit cards go through a processing center and are NOT linked to checking. Never link a checking and savings account (overdraft protection). I was working on a project with RIT when they developed the new bills. The metallic strip is for validation and detection (for travel limit). Cannot really 'read' the amount of money in the wallet. Did some work years ago with REI on bill counter/verifiers that were optical - fast and accurate. Actually, most counterfeit US$ is outside the US where it doesn't get verified. Our bills get recycled rapidly so they go through the Fed process.