If you've ever paid with coins, e.g. quarter dollars, it shouldn't be difficult to see how this can be done. For smaller transactions it is less risky to skip verification of every bit of money. For larger transactions it is more important. If you've ever paid with official government bank notes, you'll see many cashiers treat you like a criminal by running some marker across the bill and holding it up to the light. It takes a few seconds and is usually unnecessary but a similar procedure can be done if there is suspicion. If one percent of the manpower that has gone into bitcoin-related software and hardware went into automating this kind of precious metals verification, we probably could be using gold and silver today in person with less hassle than bitcoin.