Watch List notes:

Greek Coins
Potidaea

Tetradrachm circa 500-480, AR 16.78 g. Poseidon Hippios, holding trident, on horse at pace to r.; beneath, seven-rayed star. Rev. Rough incuse square diagonally divided. AMNG III, pl. XX, 20. SNG ANS 689. Mitchiner 1010.
Very rare and in exceptional condition for the issue. Struck on unusually good metal
and with a lovely old cabinet tone. Extremely fine
From a private American collection and purchased in in the early 90's in an auction we have been unable to identify.