Commodus With A Sarapis/Serapis And Cerberus Reverse.

There are 19 pages in the RPC online catalogue of Sarapis seated with Cerberus at his feet, with a total of 363 entries. Most of them are in Egypt, as are copies of the famous statue of Serapis in the Serapeum of Alexandria, attributed to the sculptor Bryaxis who was active towards the end of the fourth century BC.

I found this coin of Commodus from Pergamum to be interesting as the original collector's tag said "small person in front" which the vendor had corrected to "Cerberus". It would have been extremely difficult for an engraver to replicate a three-headed Cerberus in such a small size, but it does indeed resemble a small person with large ears.

Extracts from the Galleria Borghese site describing the statue in the Borghese Collection, which was Purchased by the Italian State in 1902:
Wolfang Helbig identified the statue as a representation of Serapis and a copy of the original by the sculptor Bryaxis in the Serapeum of Alexandria. In 1925, Walther Amelung furthered Helbig's analysis, concentrating on the figure of Cerberus (Amelung 1913, pp. 251-252, no. 1563). According to Macrobius, the animal's three heads (a wolf, a lion and a dog) symbolically represent the tripartite division of Time into past, present and future, with Serapis as the Sun (Macrobius, Saturn., 1.20.13). In an exhaustive study of the god and Cerberus in particular, aimed to reconstruct the Alexandrian original and published in 1973, Wilhelm Hornbostel identified two typological categories for the animal: the first, more common, depicting him with the heads of three different types of dog; the second, rarer, with a lion head.

The god is portrayed seated on a plain throne with a high, broad back and a low stool; he wears a long unbelted tunic and a mantle that falls from his left shoulder over his chest and ends elegantly draped over his legs. He wears sandals called krepídes on his feet. His left arm is raised to hold the sceptre and his right arm, restored, is bent and facing forward, his hand holding a patera.

Serapis, extracts from the Bibliotheca Alexandrina Antiquities Museum site:
Serapis is the same Egyptian deity Usir-Hapy (the deceased Apis bull united with Osiris) worshipped in Memphis, and known to the Greeks as Usir-Apis. His cult started during the 26th Dynasty. At the beginning he was worshipped in the form of the sacred bull Apis. When Osir-Apis became the official god of the Ptolemaic Empire, Zeus was selected to incarnate him, to avoid the animal form which was inconvenient for the Greeks. To make the pronunciation easier he became to be known as Serapis. Isis and Harpocrates (Horus the Child) were also selected with Serapis to form a sacred triad. Thus, Serapis was meant to form a bridge between the Greek and Egyptian religions in a new age in which their respective gods were brought face-to-face with each other, so that both Egyptians and Greeks could find unity in a specific supreme entity. The cult of Serapis lasted well into the Roman period, and his temples spread all over the Mediterranean basin.

Serapis as a healing god
When Serapis had once been established by Ptolemy I in Alexandria as a chief god of the Egyptians and the Greeks, and had been presented in the visible similarity of a Greek god, he came to receive attributes analogous to one or other of the ancestral Greek gods. He became specifically assimilated to Asklepios as a god of healing. Sick men might sleep in his temple and receive instructions through dreaming regarding their case. These attributes may have been quite early attached by the Greeks to Serapis.

Cult centers
The center of worship of Serapis in Ptolemaic times was Alexandria at the great Serapeum. This temple was considered a pilgrimage site throughout the Mediterranean area, until it was destroyed by order of Emperor Theodosius in 389 CE. The Serapeum, which Ptolemy I founded, was probably on the Hill of Rhakotis. The temple in question was rebuilt during the reign of Ptolemy III (246-222 BCE).
The cult also existed in the late Pharaonic temple complex, later known as the Memphis Serapeum, which was rebuilt during the Pharaonic Period by Nectanebo I and Nectanebo II. This building was the destination of the crowds of pilgrims who sought oracle healing while sleeping inside the god's temple.

Commodus. Pergamum, Mysia. (177-192 AD)
Obverse: Laureate bust of Commodus right, wearing cuirass and paludamentum. Obverse inscription: AV KOMOΔOC. Reverse; Sarapis seated left, wearing kalathos, holding long sceptre and extending right hand over Cerberus sitting at his feet. Reverse inscription: ΠHPΓAMHN. Bronze. Diameter: 20 mm. Weight: 5.00 gr.
Reference: RPC 4 3274

As there were only two images of this type in the RPC database, the images of this coin were uploaded: https://rpc.ashmus.ox.ac.uk/coins/4/3274