Byzantine gold coins of the seventh through the tenth centuries provide evidence that tends to confirm the known and speculated history of the Shroud: where it was located, who had access to it, when it was out of circulation, and when it reappeared. The degree of fidelity to the Shroud face image indicates generally whether or not the engraver had access to the image itself.
You will remember that the Shroud as the Mandylion was hidden in the city wall of Edessa from A.D. 57 to about 525. In the sixth and seventh centuries, Edessa was part of the Byzantine Empire, so the Mandylion would have been accessible to Byzantine artists. The first coins to carry the depiction of Jesus were produced under Justinian II during the years 692-695. These were gold coins of at least two different weights, the larger solidus and the smaller tremissis (one-third the weight of the solidus), and they were in common usage. They are numismatic icons, and their depictions are the ones most congruent with the Shroud.
The tremissis coin has a depiction of Jesus on it that looks crude, not at all attractive, and your first thought would be that the die cutter must have been inexperienced or otherwise not skilled. However, if you carefully compare the tremissis face with the Shroud face, you will see that the tremissis depiction is a direct copy from the Shroud and has one hundred eighty-eight points of congruence with it. Certain features can be seen clearly, too small to be observed and copied without magnification, overly each other exactly, for instance, whisker on whisker.
The second coin that we compared with the Shroud face image was a solidus. The face image on one solidus is nine millimeters (about three-eighths inch) from the top of the head to the point of the beard. There is no doubt that the depiction thereon is that of Jesus, for the coin is inscribed Jesu Christu, Rex Regnantium (Jesus Christ, King of Kings). It has and amazing one hundred forty-five points of congruence with the Shroud face image. The detail is incredible, much of it too small to be seen with the unaided eye. It began to dawn on us that both coins had to have been designed by the same die cutter, and that this person must have been one of the most skilled artists of all time to have been able to produce so many details so accurately in such tiny areas. How a seventh-century iconographer ever got such detail engraved in so small a space is beyond our understanding. Much of it you cannot even see with the unaided eye.
Our speculation is that the tremissis may have been a prototypic coin. The Emperor may have commissioned the issuing of a coin with the likeness of Jesus and told his iconographer/engraver/die cutter to produce as accurate a copy of the face image believed to be that of Jesus “not made with hands” as possible. This the die cutter did for the tremissis, but it may have been that the Emperor was unhappy with the crude appearance and therefore instructed his die cutter to try again and this time produce an image that would be not only accurate but also attractive. In any case, except for this one direct copy, all the other coins bear what we might call derived images, that is, images that are accurately based on the Shroud face image, but are also artistically made more complete and pleasing.
Solidus coins struck during the second reign of Justinian II, 705-711, also carry depictions of Jesus, but the die cutters quite obviously did not have direct access to the Mandylion/Shroud to use as a model, for the coin images are much different. One coin that we have from these years has only fifteen points of congruence with the Shroud face image, far below the number needed to establish identity. The reason for the inaccessibility of the Mandylion/Shroud face image to the artists of Constantinople during this time is that the Mandylion was still in Edessa and at that time Edessa was in Muslim hands.
With the onset of the iconoclastic period in the Eastern Church in 726, Emperor Leo III forbade the use of religious images. No further images of Jesus appeared on Byzantine coins until the Church at the Council of Nicea settled the use of images in 842. Under Emperor Michael III, the image of Jesus reappeared on the solidus coins in 843, but the image was very crude. It grossly resembled the images on the coins of Justinian II in 692-695, but had only about twenty points of congruence with the Shroud image. We feel that the die cutters were probably using the coins of Justinian II for their model rather than the Shroud face image itself, and thus they missed most of the fine details that give evidence of direct access to the original. From 843 until 944, the face image of Jesus appeared on most of the Byzantine gold solidi, but the images were increasingly crude and inaccurate.
Then another gold solidus from Constantine VII appeared about 945 with a face image of Jesus only seven and one-half millimeters high but with over ninety points of congruence. This change in fidelity to the Shroud face image corresponds to the bringing of the Mandylion from Edessa to Constantinople in 945, when again it would have been available to artists.