I was walking around my computer room with the black light (otherwise the room was dark) looking for my cat's "accident" and one of my Mastercards was laying on the desk. As I walked by the desk, the letters MC were glowing on the front of my card. I got out my other Mastercards, and sure enough when exposed to black light the letters MC are visible on the face of the card. I started pulling other cards out of my wallet. My Visa cards all have the image of the bird that's in the hologram on the bottom right embossed on the front of the card, only visible to black light. My Cobalt card says AMEX across the top when put under the light.