What is the earliest known battery

We have evidence that batteries were not unknown in the ancient world. The Parthians were a race living in the Mediterranean about 2000 years ago, from ca 300 bc until ad 224, when they were wiped out by the Romans. They are mentioned in the Bible, e.g. see The Acts of the Apostles, Chapter 2. 

A device was found in 1936 near what is now modem Baghdad, the capital of Iraq. It consisted of a copper cylinder housing a central iron rod. The identity of the ionic electrolyte is now wholly unknown. The device was held together with asphalt as glue. 

If the copper was tarnished and the iron was rusty (i.e. each was covered with a layer of oxide), then an approximate emf for this 2000-year-old battery would probably be in the range 0.6-0.7 V. We do not know what the battery was used for. 

One of the first batteries in recent times was the Daniell cell, 

Zn Zn2+ Cu2+ Cu. This battery comprised two concentric terracotta pots, the outer pot containing a zinc solution and the inner pot containing a copper solution. Metallic rods of copper and 

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