This piece started out as an original that I handmade in oil-based clay. I use silicone rubber to make a mold, capturing every detail from my original sculpt. The mold is poured as a solid piece with urethane resin, and then cleaned up, and coated with white primer to allow for easier painting. It can be left white as-is, or you can paint it however you choose (acrylics work the best).
I often have painted skull magnets available in the Etsy shop. I also have completely blank mini skulls with flat backs, like this but without the magnet or primer, which can be used for costume props or other decoration.