Most gems of the Classical Period are either in the form of a scarab or a scaraboid.  More rarely the Greeks used a sliced cylinder or a barrel, as in the example presented here. Despite the cylindrical form, Greek barrel seals were not meant to be rolled in the Near Eastern manner but instead were engraved to function as a stamp seal, similar to the more popular scarabs and scaraboids.  Several other barrel seals are also engraved with a heron, a subject well suited for the elongated available field (see pp. 199-200 and pls. 518-519 in Boardman, Greek Gems and Finger Rings). Here the heron stands on one leg on a short groundline, with the other slightly raised, its head lowered as if foraging.