Maybe an unusual way to present a coin, but it shows clearly the pinpoint-like tininess and clear detail of my smallest coin, noted as a silver 1/96 stater or tetartemorion (that would be 1/4 of an obol, but I might be erring). It is from Erythrai (though some think it might be Miletos, which is 100 km to the south).
Erythrai (or Erythrae) was always a small polis, at the Anatolian coast opposite the island Chios. It dates from 520-480 BC, before the city joined the Delian League, with Athens and against the Peloponnesos under Sparta.
The obverse of this silver coin shows a whirl, the reverse a rosette. A whirlpool, naturally, was an interesting subject for seafaring folks like the Greeks. But the city of Erythrai apparently was famous for its millstones, so this might be a depiction of a product of which it was proud.
The diameter is 4 mm, the weight .12 gr.
-- Paul