Desperate people spending their coin collections made when they were kids?
When I was a kid I had all kinds of old coins in those blue folders. I wanted a stupid guinea pig so I used the coins to buy one. Thing was nasty and loved to squeal and bite. I was happy when it died. Wish I still had the coins. Not worth all that much, but still...
Back in the 70s I talked with a guy who ran a gas station during the Depression. He showed me a handful of badly worn coins dating back to the 1870s that he said people used to pay for their gas. Or, it could be dumb robbers spending a stolen collection as common money. Years ago we had a detective talk to our coin club. Someone said they found a near-mint Standing Liberty quarter in circulation and he posited that scenario, which made sense.
He also suggested to people who saved rolls of coins to scratch your name/initials on a junk coin and insert it into the roll. If they are ever stolen and they catch the thief who claims they are his, you can ask him how your ID got on his coins.
I blame the Coin Star machines. People just throw their change in a jar. When the jar gets full they run to the grocery store and pour the coins into the machine without looking at them. The coins go to the bank counting machine and get rolled up and re-issued. No one even looks at the coins. A few months ago I got a silver quarter in change from the Piggly Wiggly. Before that I got a liberty head "V" nickle in change. As someone said earlier, wheat pennies are become common in change.