Watch List notes:

L. Marcius Philippus. 57 B.C. AR denarius (18 mm, 3.89 g, 6 h). Rome. [ANCVS] below, diademed head of Ancus Marcius right; behind, lituus / P[HIL]IPPVS on left, equestrian statue right on arcade of five arches; within arches, [A]-Q-V-A (MAR). Crawford 425/1; Sydenham 919; Marcia 18. Lightly toned. Good fine.

From the Big Sky Collection.

The obverse of portrays the diademed head of Ancus Marcius, the fourth King of Rome. He was the progenitor of the Marcia gens which had at least two branches, the Philippi and the Reges. Although L. Marcius Philippus belonged to the Philippi branch of the Marcii, he appropriated an event from the Reges branch as it was the praetor Quintus Marcius Rex who built the Aqua Marcia in 144-140 BC. Perhaps the moneyer was being a little devious to illustrate something he could not rightfully claim; the man in the street probably would simply assume that it was the moneyer's ancestor who had supplied Rome with it's greatest source of potable water.