Circulated is a term to describe a coin that is found in change currently. Coins in circulation may be over a century old; as long as they have the same or similar design and face value.
Coins in the Brazilian Real do not follow the trend. Many of their old coins, which are stainless steel, are not Uncirculated, even though their value does not match the face value. Some currencies may keep coins in circulation for a while, which are later ceased.
In numismatica, coins that have not been issued for a specific year are not considered circulated. Pennies in the Pound Sterling were circulated from 1968-71 but were not issued (not including the GBP 1970 -/1 Shilling proof penny). Therefore, they are considered uncirculated.