Watch List notes:

CYCLADES, Keos, Karthaia, (c.510-490/80 B.C.), silver stater, (11.73 g), obv. amphora within border, rev. quadripartite incuse square, (S.-, Sheedy 20-2 var. (dolphin), Papageorgiadou-Banis 15-6 var. (dolphin), see Lanz 162, lot 67 (same dies). Lightly toned, some surface granularity, very fine and extremely rare.

Ex CNG CNR purchase, #460978 with ticket.
This extremely rare issue is an unpublished variant.