Like10 to15 years ago people used public coin phone booths to do their important calls on the go, on a daily bases it was familiar to see waiting line in front of the cabinet waiting for their turn.
Coin phones,
Even though calls was clearly cheap, it was common to see some metal circles simulates the coin –Coin fraud– weight and size, in order to cheat the cabinet and establish a free phone call, and guess what? This fake coins was returned to other customers as change after finishing a call. You may also recall that coins connected to a wire where the user can pull it back after finishing his call.