Nondestructive testing would be better.
But when I speak of data, I am talking about the information content in the image itself, which is not something possible to encode, certainly not in the 14th century. Do you dispute the information content in the image?
information content in the image? Hand holes in the right place, no visible brush strokes, that sort of thing? No dispute there, but nothing much more, either. The thing appeared, like magic, after a thousand years of mystery and myth; I have no confidence in the authenticity of so valuable and convenient an artifact discovered so long after the fact.