Tetarteron

Ever since Emperor Constantine I (r. 306–337), the Byzantine Empire's main coinage had been the high-quality solidus or nomisma, which had remained standard in weight and gold content through the centuries.

[2] Modern scholars have alternatively suggested that the tetarteron was an imitation of the Muslim gold dinar, for use in the eastern provinces recently reconquered from the Arabs, or perhaps an element of an abortive monetary reform that intended to replace the histamenon altogether.

During the later reign of Basil II (r. 976–1025), the tetarteron began to be minted in a thicker and smaller form, while the histamenon conversely became thinner and wider.

[8] However, starting with Michael IV (r. 1034–1041), who was a former money lender, the gold content began to be increasingly lowered and the coins debased.

[11] The new coin, flat, weighing circa 4 grams and valued (at least initially) at 864 to the gold hyperpyron, was struck in great quantities and in a large variety of designs, especially in the 12th century.