Enamel during a process that requires eighty hrs. It comes in 18-karat white gold with numerous shades of eco-friendly or in 18-karat pink gold with blue hues, both equally accented with diamonds. The bottom steel of each is first sealed with a clear enamel then layers of opaque white enamel https://www.watchesworld.com/from-sean-to-daniel-tracing-the-evolution-of-james-bonds-iconic-watch-collection/