CNG Auction 5, 1367
Sold for $63.80

Gallienus. 253-268 AD. Antoninianus (2.85 gm). Struck 258 AD. Mediolanum mint.
GALLIENVS AVG, radiate and cuirassed bust right / 
LEG IIXX VI P VI F, capricorn right. 

RIC V pt. 1, 362; RSC 542a.

The 18th Legion was destroyed with Varus and never reformed, so the legend IIXX may be the engraver's error for XXII, the capricorn being the badge of the 22nd Legion.