“They seem to hinge on similarities of depictions on coins of the era among other things.”
That’s not really the best evidence. One of the codices has Greek text that appears to have been copied, word for word, from a tombstone on display in a museum in Jordan, but the copier did not know Greek, because they confused the letters lambda and alpha. Only a fragment of the text on the tombstone was copied, and this was repeated over and over, in a nonsensical fashion. Also, that codex was originally claimed to be found in Egypt, but now it’s popped up again with the lead codices and claimed to have been found in Jordan.
