Diamond Pencil, Wartski
Diamond and steel
consisting of a blackened steel grip embellished with a red silk tassel, the tip mounted with a diamond, the point of which can be used to engrave glass.
The tradition of writing on glass with diamonds is very ancient. Similar pencils were used by European royalty in the Tower of London, Sandringham House (Norfolk) and the Hermitage Palace in St Petersburg. Perhaps most famously Princess Elizabeth, later to become Queen Elizabeth I, wrote on a window using a diamond when she was under house arrest at Woodstock Palace.