Cartier pen, I believe it is the Diabolo Pen. From Cartier's site: PRODUCT DESCRIPTION Diabolo de Cartier ballpoint pen in black composite, palladium-finish details, blue resin cabochon. Dimension: 136.5 mm high. ABOUT THE COLLECTION Available in lacquer, mother-of-pearl, solid gold, hardstone and leather-encased versions, Cartier pens are a signature of unique taste in fine accessories. These most precious writing instruments offer a perfectly proportioned shaft and cap and a 750-gold flexible nib.