Part of a collection of 15th-18th Century French graffiti documented at the Chateau de la Roche-Guyon, France during the summer of 2018. Documentation done with Sony A7III and processed in Reality Capture from 119 photos. GDH ID Graffiti 6. Mason's mark. A Greek cross is represented, characterized by having arms of equal length. It’s one of the most common Christian forms, in common use by the 4th century.