When filled with vinegar - or any other electrolytic solution - the jar produces about 1.1 volts.
It was found in Khujut Rabu just outside Baghdad, composed of a clay jar with a stopper made of asphalt.
Sticking through the asphalt is an iron rod surrounded by a copper cylinder.

There is no written record as to the exact function of the jar, but the best guess is that it was a type of battery. Scientists believe the batteries (if that is their correct function) were used to electroplate items such as putting a layer of one metal (gold) onto the surface of another (silver),
a method still practiced in Iraq today.