What is the meaning of Counterpart?

Either of two parts that fit together, or complement one another.

A duplicate of a legal document.

One who or that which resembles another. (Can we add an example for this sense?)

One who or that which has corresponding functions or characteristics.

Either half of a flattened fossil when the rock has split along the plane of the fossil.

To counterbalance. (Can we add an example for this sense?)

Source: wiktionary.org