Public Domain edit
On further thought, I believe this image and its twin are public domain. They are x-ray images of a leaf of paper created in the 15th century showing the watermark. Although a watermark pattern may show enough creativity to be subject to copyright, this watermark pattern was created in the 15th century and is now PD. A photograph of a two-dimensional object that is PD also is PD. An x-ray showing the PD watermark also should be. In addition, it is Wikimedia policy that x-rays are not copyrightable. See wikimedia:Wikilegal/Copyright of X-ray Images. Ecphora (talk) 20:54, 8 March 2017 (UTC)
