Watch List notes:

Mysia, Pergamon(?). L. Sempronius Atratinus. Quaestor, ca. 42-39 B.C. AR cistophoric tetradrachm (27 mm, 12.83 g, 7 h). Serpent emerging from cista mystica with lid ajar; all within ivy wreath / Bow case between two serpents; above, monogram of Atratinus; in left field, Q; in right field, thyrsos. Stumpf 3; SNG BN 1767. Reverse a little off center. Good very fine.

Although this type is catalogued under Pergamon in SNG BN, the mint is not certain. Atratinus struck two varieties of cistophori during his tenure as Quaestor in Asia, those like the specimen here with a serpent-entwined thyrsos in the right field of the reverse, and others with a torch. It seems logical to presume that cistophori in Atratinus' name having the thyrsos were struck at Pergamon since the symbol is common on cistophori from that mint, while those with the torch were minted at Ephesos, but this is disproved by obverse die links between the two varieties.