Typically a phone machine token. From memory, this system emerged in either France or Germany in the 1930's and spread across the world. It was convenient in places with unstable currencies, like Italy or Palestine/Israel where prices would noticeable inflate, so it was easier to just change the price of the token.
Here in Australia, our pound and the the dollar was always relatively stable, so your phone machines accepted legal tender coins. Local calls are now free actually (forgot my phone on a date the other day).
These things are collectable. If you zoom in on a particular theme, such as the Asimon tokens from Israel for example, they have dates varieties, etc. Just like coins.