CIMRM 828 - Castor-ware beaker. St Albans, Britain

First two images © St. Albans Museums Service, to whom many thanks. Other images taken by Roger Pearse at the Verulamium Museum, 13th August 2013. Note Mithras' garment is starry.

From: Vivienne J. Walters, The cult of Mithras in the Roman provinces of Gaul, p.40:

A Castor ware beaker from Verulamium, with green-brown colour coat, and decorated with figures en barbotine, has been dated to the late second century or early third century A.D. It depicts a series of gods with, on the left, in profile, a figure dressed in a tunic, decorated with stars and crosses, wearing a Phrygian cap and holding a bow, ? Mithras. A second figure depicts Hercules, a lion's skin over his arm, and the winged feet of the missing third figure probably represent Mercury : one more pair of feet also survive.[1]
[1] Archaeologia, XC. 1944, pp. 121-2. fig. 20, no. 1; J. M. C. Toynbee, Art in Roman Britain, London 1962, p. 190, no. 157, pl. 190.

"Castor ware" is an alias for Nene Valley Colour-Coated ware, according to Potsherd: the atlas of Roman pottery.

CIMRM entry

828.
In the Verulamium Museum is a Castor-vase (H. 0.21) which was discovered in a public building (insula XVII) opposite the Theatre (cf. K. M. Richardson in Archaeologia, XC, 1944, 121).
On the vase with barbotine-decoration, three persons are represented:
1) The naked lower part of a man's body with a lion's-hide over his arm (Hercules).
2) The naked lower part of a man's body with winged feet (Mercurius).
3) Man walking to the right in Phrygian cap and with a bow in his r.h. Dressed in a short tunic, on which seven stars are visible at the bottom. On his breast two cross-wise belts. If the person, as assumed, would indeed represent Mithras, then it can only be an unusual representation of Mithras as an archer.