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Coins were thus denominated, from the cista, or mystical baskets, used in the worship of Bacchus, and which were always found figured upon them. In its original sense the term of cistophorus and cistophera were applied to him or her who, in the mysteries of Bacchus, or ofCeres and of Proserpine, carried the cista, which enclosed the sacred serpent. Amongst the Greeks it was the custom for young girls of high rank to bear this mystic chest at public festivals. The medals called cistophori were coined by authority in reference to the feasts of Bacchus, and became the peculiar symbol of Asia.
http://www.forumancientcoins.com/numiswiki/view.asp?key=cistophori
Above coins of Eumenes of Pergamum…