Both PB ranges were based on Phil Barker's books Armies of the Macedonian and Punic Wars and Armies and Enemies of Imperial Rome. This figure is taken from illustration 20 in AMPW.
The 's' designation was used to distinguish the newer 25mm style of models from the preceding, smaller 1/72nd range. The transition was soon complete and the 's' - special - was dropped from the figure codes thereafter.
The Cardaces were apparently armed and equipped to fight in a comparable fashion to hoplites - or possibly peltasts - and were an innovation aimed at fielding a body of native close fighting infantry. The model doesn't look terrible convinced.