Watch List notes:

ROMAN AND BYZANTINE COINS

Ionia, Magnesia ad Maeandrum. Gordian III, 238-244. Pentassarion (Bronze, 34mm, 27.59 g 6), A. Demoneikos Prothoos, grammateus. ΑΥΤ Κ Μ ΑΝΤ ΓΟΡΔΙΑΝΟC Laureate, draped and cuirassed bust of Gordian III to right, seen from behind. Rev. ΕΠΙ ΔΗΜΟΝΕΙΚΟΥ / ΜΑΓΝΗΤΩΝ Selene in biga of bulls rushing to left. RPC 532. Schultz 432. A bold piece with a green patina. Struck on a very broad flan with dies that are clearly considerably smaller. Good very fine.

Ex Gorny & Mosch 181, 12 October 2009, 1775.
What is quite exciting about this coin is its flan: obviously much too large for its dies. This must have occurred by mistake in the mint, when a worker took a flan prepared for a heptassarion instead of a pentassarion (those would have been approximately 29 mm in diameter instead of nearly 35 mm as here). As a result, this beautifully struck piece has a remarkably medallic aspect!