The Limited Edition Mystery Masterpiece, a joint creation between Montblanc and Van Cleef & Arpels is one amazing pen. Both companies celebrated their centennials in 2006 and the pen is meant to showcase each company's area of expertise. There are three variations, set either with rubies, sapphires or emeralds, and accented by diamonds. There are three versions of each pen for a total of nine. Each pen has 840 diamonds and over 20 carats of gemstones set in a Van Cleef & Arpels patented "Mystery Setting" that conceals the stone settings. A grove is made on the cutlet, the bottom facet of the stone, which is then slid onto the threads of the lattice design so that the stones can be held in place side by side without any visible support. The Mystery sells for $730,000, making it the most expensive writing instrument ever created.