Cr. 408/1a C Calpurnius Piso L.f. Frugi, 61 B.C.
Roman Republic AR Denarius(3.75g), Caius Calpurnius Piso L.f. Frugi, 61 BC, Rome Mint. Laureate head of Apollo right; Stork or egret behind / Horseman, holding whip and reins, on horse galloping right; lituus above, C·PISO·L·F·FRVG below. Crawford 408/1a(67 B.C.), dies O5/R5
From the intro of Charles Hersh's die study on this type, published in Numismatic Chronicle 1976, which is the most complete study ever completed for this issue:
Caius was the scion of an old plebeian family. His father was Lucius Calpurnius Piso L.F. Frugi, who was moneyer during the Social War in 90 B.C. and was elected praetor in 74 B.C. Caius was himself born in 87 B.C. and in 67-66 B.C. he was betrothed to Tullia, the only daughter of Marcus Tullius Cicero, the orator and statesman. The couple were married in 63 B.C., when Cicero was consul. Caius was elected quaestor in 58 B.C., during the consulship of his kinsman, Lucius Calpurnius Piso L. F. Caesoninus. While in office he devoted his efforts to trying to obtain the recall of Cicero from banishment in Macedonia, whither he had gone following the legislation sponsored by his enemy, Publius Clodius Pulcher. At the end of his quaestorship Caius was allotted the provinces of Pontus and Bithynia, but he remained in Rome to continue his efforts on Cicero’s behalf. He died during the early summer of 56 B.C., before the return of Cicero to Italy on 5 August 57 B.C., following his recall.
Caius probably was a moneyer during 63 B.C., when Cicero was consul. The only denomination of coins he struck was the denarius and he used the same obverse and reverse types as on the denarii of his father. The obverse had as its type the head of Apollo, while the reverse depicted a naked horseman. The latter is a direct reference to the Ludi Apollinares, the annual celebration of which was proposed by an ancestor of the moneyer, C. Calpurnius Piso, who was praetor in 211 B.C., the year following the establishment of the games.
This coin comes from what Hersh refers to as a "section 1" obverse die, with a laureate head of Apollo facing right, and as Hersh points out, a more refined, Hellenistic-influenced style than the obverses of other sections. The obverse symbol is variously described as a stork or heron - I don't know enough about birds to have a strong opinion, but I'd certainly like to hear if you do. The reverse symbol is a lituus, a curved staff used for ceremonial purposes to mark out ritual spaces in the sky.