A silver tetradrachm, minted in Syracuse circa 485-478 BC under the reign of Gelon I, is valued at $75,000 ahead of a sale at the Classical Numismatic Group.
It will headline an online auction of Ancient, World and British coins on May 14.
The coin was one of a large number issued to fund the war against the Carthaginians, who were defeated at Himeria in 480 BC.
In the aftermath of the conflict, the city became enormously wealthy - encouraging an influx of artists and craftspeople. Later Syracucian tetradrachms (from the third century BC onward) are considered the high water mark of Grecian coinage.
This archaic example features a charioteer overseen by a winged Nike, while the obverse shows a bust of the nymph Arethusa surrounded by four dolphins.
A gold pentadrachm of Ptolemy III is valued at $75,000.
The lot dates to 224-221 BC and displays a bust of Berenice II, wife of Ptolemy, who was murdered by her son Ptolemy IV in 221 BC.
She became a popular mythological figure in ancient Egypt after a lock of her hair mysteriously disappeared from a temple in Syria. It was said to have formed a new constellation.
The coin is exceptionally well centred and struck, with minimal cracks and other markings.
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