Studio On Fire custom duplexed the card from two colors. The black side is Skin Black 141lb Cover. That is pasted to Skin White 141lb Cover for a total thickness of 280lb Cover.
Production went something like this… The black stock is hot foil stamped in a clear gloss foil and a mirror finish metallic silver. The white stock is letterpress printed in metallic silver ink. Then the black and white sheets are pasted together in register into a heavy duplex sheet. Those sheets are covered with a protective mask on both sides. The masked sheets are laser cut into the custom shaped business cards and the protective mask is removed.