As with all the 'PB' range it is derived from Phil Barker's pair of books Armies of the Macedonian and Punic Wars and Armies and Enemies of Imperial Rome. PBC standing for Phil Barker Cavalry. This figure corresponds with illustration 55 in AMPW.
He is riding the ubiquitous PBH 65-217 which is listed as two different horses in the 72/73 catalogue: PBH 65 Cavalry Horse and PBH 217 Roman Cavalry Horse 1st and 2nd Centuries AD. The code is stamped on the base in the usual way.