Brass carving of Leonardo da Vinci's famous Vitruvian Man. Intaglio Printing (Engraving): Because the image is carved into the metal rather than raised, this is an intaglio printing plate or an industrial stamping die. Leather or Foil Stamping: This could also be a female die used for stamping book covers or leather goods. A matching raised piece would press the leather down into these deep grooves to create a crisp, raised 3D design on the final product. The corner holes were used to screw the plate tightly into a press machine so it wouldn't shift under the immense pressure required for intaglio or stamping work. The back markings: The handwritten "London" text on the reverse side is a common workshop or inventory mark used by printers, blockmakers, or publishers to track where the asset was made, filed, or scheduled to be shipped.