The South Carolina was originally built as the Dutch ship L'Indien and was actually leased from Luxembourg which appears to have been a device used to give France deniability. [Middlebrook, p. 3]
He also indicates that the initial crew size was about 550 but that was on the initial voyage from the Texel. The crew size given at the time of capture in December, 1782 was only 430.
Middlebrook quotes several contemporary official records which substantiate that the South Carolina was indeed a very imposing frigate and was closer to being a 4th rate than a 5th rate ship-possible a two decker similar to HMS Serapis
She was frigate-built, but from forty to fifty per cent. more powerful than any regular frigate then afloat; the equal in fact of any forty-four-gun ship on two decks in that period, and not much inferior to most ships of fifty guns.
When Jones left the United States in the Ranger, it was understood, and in fact ordered, by the Marine Committee that he should, on arriving in France, take command of the new ship building at Amsterdam, for which Silas Deane had contracted in 1776. The commissioners -- at least Deane and Franklin -- had made every effort to keep the actual character of this ship a secret from the British Government. The contract for her construction had been signed on behalf of the United States by a Captain Gillon, in the service of the Dutch East India Company, who was employed by the commissioners to supervise her construction. Gillon, however, was himself "supervised" by Charles Frederick Dumas, secret agent of the Colonies in Holland, and the bills were paid through Dumas's banker. This ship, then known as the Indien, was of peculiar construction, and her general plans were those furnished to the Marine Committee by Jones in the fall of 1775 in connection with the new frigates then authorized.
She had been on the stocks since December, 1776, and when Jones arrived in France the December following, the Indien was nearly ready to launch. However, her guns and ammunition were to be placed on board at l'Orient as soon as she could be brought round there from Amsterdam. But shortly after she was launched the British Minister to the Netherlands denounced her to the States-General as an American ship-of-war in disguise, and demanded that she be detained in Dutch waters for "meditated breach of neutrality." The commissioners were dumb-founded at this exposure of their plans, but could do nothing, as the States-General was then under British influence, and after fruitless efforts to get possession of the ship, they sold her to the King of France for a price nearly sufficient to reimburse them for the outlay already made under the contract. This sale was concluded only ten or twelve days before Jones arrived in France with the Ranger. In the course of his investigation, before referred to, Jones ascertained beyond question that the secrets of the commissioners in regard to the Indien had been betrayed to the British Government by Arthur Lee's private secretary, Thornton; also that he had actually furnished the British Foreign Office with documents from the secret files of the commissioners, unquestionably proving the real character of the ship; documents which the British Minister had laid before the States-General.
To maintain neutrality, and to escape Great Britain's ire, the Dutch demanded the ship be chartered through the King of France. After American acceptance of these terms, the L'Indien sailed from Amsterdam and was renamed the South Carolina with Captain Joyner in command. The heavily armed frigate sailed into international waters without incident. But, in the gray dawn of 19 December 1783 the Officer of the Watch spied a British squadron closing in on the South Carolina. A chase began with South Carolina masterfully out-maneuvering and outrunning the British squadron. By midday, only the HMS Quebec under Captain Christopher Mason, and HMS Diomedes under Captain Matthew Squire, remained in dogged pursuit. Sadly, the valiant efforts of the South Carolina's captain and crew were to no avail; the British ships eventually overtook and captured her
Howard Chapelle, The History of the American Sailing Navy: the Ships and their Development (New York: Norton, 1949)