The author is clearly hostile to Callistus and this is one of the strongest indicators that Hippolytus is the author of the Philosophumena (as both are presumed to have been rival bishops of Rome). Yet for the moment, let's at least accept the idea that Clement, Jerome and Cassian seem to open the door to the idea that the money changer 'testing' coins for their purity was related to the assigning of bishops and presbyters to their role in the Church - is it possible then that the association of Carpophorus with as a 'banker' and 'banking' might actually have originally been an allusion to him being a bishop in the Church of Rome.
Here is the original material from the Philosophumena:
Callistus happened to be a domestic of one Carpophorus, a man of the faith belonging to the household of Caesar.
Οίκέτης ετύγχανε Καρποφόρου τινός, ανδρός πιστοΰ όντος έκ τής Καίσαρος οικίας,
To this Callistus, as being of the faith, Carpophorus committed no inconsiderable amount of money, and directed him to bring in profitable returns from the banking business.
τούτω ό Καρποφόρος, άτε δή ώς πιστώ, χρήμα ούκ ολίγον κατεπίστευσεν, έπαγγειλάμενος κέρδος προσοίσειν έκ πραγματείας τραπεζιτικής
And he, receiving the money, tried a bank in what is called the Piscina Publica.
ος λαβών τράπεζαν επεχείρησεν εν τη λεγομένη πισκινρ πουπλική,
And in process of time were entrusted to him not a few deposits by widows and brethren, under the ostensive cause of lodging their money with Carpophorus.
ω ουκ όλίγαι παραθήκαι τω χρόνια επιστεύθησαν ύπό χηρών και αδελφών προσχήματι τοΰ Καρποφόρου.
Callistus, however, made away with all, and became involved in pecuniary difficulties. And after having practised such conduct as this, there was not wanting one to tell Carpophorus, and the latter stated that he would require an account from him.
ό δέ έξαφανίσας τά πάντα ήπόρει. ού ταΰτα πράξαντος ούκ έλιπεν δς άπαγγείλη τω Καρποφόρω, ό δέ έφη άπαιτεΐν λόγους παρ' αυτού.
Callistus, perceiving these things, and suspecting danger from his master, escaped away by stealth, directing his flight towards the sea.
ταΰτα συνιδων ό Κάλλιστος και τον παρά τον δεσπότον κινδυνον ύφορώμενος, άπέδρα την φνγήν χατά θάλασσαν ποιούμενος•
And finding a vessel in Portus ready for a voyage, he went on board, intending to sail wherever she happened to be bound for.
δς ενρών πλοϊον εν τω Πόρτω ετοιμον προς άναγωγήν, δπου ετύγχανε πλέον, άνέβη πλενσόμενος.
But not even in this way could he avoid detection, for there was not wanting one who conveyed to Carpophorus intelligence of what had taken place. But Carpophorus, in accordance with the information he had received, at once repaired to the harbour (Portus), and made an effort to hurry into the vessel after Callistus. The boat, however, was anchored in the middle of the harbour; and as the ferryman was slow in his movements, Callistus, who was in the ship, had time to descry his master at a distance. And knowing that himself would be inevitably captured, he became reckless of life; and, considering his affairs to be in a desperate condition, he proceeded to cast himself into the sea. But the sailors leaped into boats and drew him out, unwilling to come, while those on shore were raising a loud cry. And thus Callistus was handed over to his master, and brought to Rome, and his master lodged him in the Pistrinum.
The point I want to bring to my readership is that we can absolutely certain that Callistus was not a 'banker' or 'money changer' at all but rather a story which originally used the agraphon from the Alexandrian secret gospel used by Clement, Origen, Dionysius and developed completely out of context (perhaps deliberately) into a story about a future Pope who 'lost all his depositors money.'
It is absolutely scandalous how badly scholars fumble this information. Their desire to avoid critically examining the information. They inevitably want to see the evidence that comes from the Church Fathers as being literal and infallible when in fact the reality is that authors like the men who penned the Philosophumena stood far away from the original evidence and completely misconstrued its original sense.
Clearly Callistus - who is said to have been bishop of Rome from 217 to 222 CE - was not a money lender at all but rather the Philosophumena's source (perhaps Hippolytus) is using the agraphon about 'testing coins' to demonstrate that Callistus faith was counterfeit. A greater question develops from our rejection also of Carpophorus as a 'money lender' or banker. Clearly Carpophorus was in fact a bishop of Rome whose church - rather than a 'bank' - resided in the Piscina Publica who tested and found Callistus's faith to be lacking (did he flee persecution in the time of Commodus?).
I have always been intrigued by the identity of this 'Carpophorus' and find it impossible not to finger him as one and the same with Pope Victor who sat as Roman Bishop during the period. It becomes absolutely clear that Carpophorus disappears from the story just as Victor is introduced. The narrative continues in fact with Carpophorus's efforts to rescue Callistus from his banishment to mines of Sardinia because of the testimony of 'Jews':
But as time wore on, as happens to take place in such cases, brethren repaired to Carpophorus, and entreated him that he would release the fugitive serf from punishment, on the plea of their alleging that Callistus acknowledged himself to have money lying to his credit with certain persons. But Carpophorus, as a devout man, said he was indifferent regarding his own property, but that he felt a concern for the deposits; for many shed tears as they remarked to him, that they had committed what they had entrusted to Callistus, under the ostensive cause of lodging the money with himself. And Carpophorus yielded to their persuasions, and gave directions for the liberation of Callistus. The latter, however, having nothing to pay, and not being able again to abscond, from the fact of his being watched, planned an artifice by which he hoped to meet death. Now, pretending that he was repairing as it were to his creditors, he hurried on their Sabbath-day to the synagogue of the Jews, who were congregated, and took his stand, and created a disturbance among them. They, however, being disturbed by him, offered him insult, and inflicted blows upon him, and dragged him before Fuscianus, who was prefect of the city. And (on being asked the cause of such treatment), they replied in the following terms: "Romans have conceded to us the privilege of publicly reading those laws of ours that have been handed down from our fathers. This person, however, by coming into (our place of worship), prevented (us so doing), by creating a disturbance among us, alleging that he is a Christian." And Fuscianus happens at the time to be on the judgment seat; and on intimating his indignation against Callistus, on account of the statements made by the Jews, there was not wanting one to go and acquaint Carpophorus concerning these transactions. And he, hastening to the judgment-seat of the prefect, exclaimed, "I implore of you, my lord Fuscianus, believe not thou this fellow; for he is not a Christian, but seeks occasion of death, having made away with a quantity of my money, as I shall prove." The Jews, however, supposing that this was a stratagem, as if Carpophorus were seeking under this pretext to liberate Callistus, with the greater enmity clamoured against him in presence of the prefect. Fuscianus, however, was swayed by these Jews, and having scourged Callistus, he gave him to be sent to a mine in Sardinia.
Indeed when the story picks up again Carpophorus completely disappears and instead we have the court of Commodus responding to an (unnamed) appeal for Callistus's release which is strangely tied in the loosest terms possible with Victor:
But after a time, there being in that place other martyrs, Marcia, a concubine of Commodus, who was a God-loving female, and desirous of performing some good work, invited into her presence the blessed Victor, who was at that time a bishop of the Church, and inquired of him what martyrs were in Sardinia. And he delivered to her the names of all, but did not give the name of Callistus, knowing the villanous acts he had ventured upon. Marcia, obtaining her request from Commodus, hands the letter of emancipation to Hyacinthus, a certain eunuch, rather advanced in life. And he, on receiving it, sailed away into Sardinia, and having delivered the letter to the person who at that time was governor of the territory, he succeeded in having the martyrs released, with the exception of Callistus. gut Callistus himself, dropping on his knees, and weeping, entreated that he likewise might obtain a release. Hyacinthus, therefore, overcome by the captive's importunity, requests the governor to grant a release, alleging that permission had been given to himself from Marcia s (to liberate Callistus), and that he would make arrangements that there should be no risk in this to him. Now (the governor) was persuaded, and liberated Callistus also. And when the latter arrived at Rome, Victor was very much grieved at what had taken place; but since he was a compassionate man, he took no action in the matter. Guarding, however, against the reproach (uttered) by many,--for the attempts made by this Callistus were not distant occurrences,--and because Carpophorus also still continued adverse, Victor sends Callistus to take up his abode in Antium, having settled on him a certain monthly allowance for food. And after Victor's death, Zephyrinus, having had Callistus as a fellow-worker in the management of his clergy, paid him respect to his own damage; and transferring this person from Antium, appointed him over the cemetery.
That Callistus eventually became Zephyrinus's deacon makes me very strongly suspect that Callistus is one and the same with the unnamed Gaius who opposed the Gospel of John and said to have lived to a very old age in third century Rome - and moreover - that Carpophorus is one and the same with Victor.
One of the most convincing reasons for accepting this is the specific mention of 'Fuscianus' as the prefect who imprisoned Callistus. Publius Fuscianus was prefect in 189 CE. The reign of Commodus ended in 192 CE. The implication being of course that there was very little time between Carpophorus's original attempts to rescue Callistus and his eventual release being secured by Marcia. It is worth noting that Pertinax, the man who succeeded Commodus as Emperor, was Fuscianus's successor as prefect from 189 - 192.
It is also worth noting that we have an inscription from a sepulcher which Rossi identifies as belonging to our Carpophorus:
And there is extant an inscription of a certain Carpophorus beginning in this very way (M. Aurel. Augg. Liberti = redeemed by the Emperor Marcus Aurelius). It seems highly probable that this is a monument or epitaph of the Carpophorus of our story. (Roma sotterranea: or, An account of the Roman catacombs p. 499)
Harnack identifies the person as very wealthy. The Piscina Publica was eventually replaced by the baths of Caracalla.
