How about an inkless pen that writes indefinitely on almost any paper? The Metal Pen, an 8 cm stainless steel writing instrument with a screw-on top, does exactly that. The pen's solid metal 'nib' consists of a metal alloy that leaves a mark on most paper types. On conventional photocopying paper, the pen makes a precise line that looks as if it were made by a pencil, but one that doesn't smudge and can't be rubbed out.

During Classical times, metal styli (sharp, pointed writing, marking, or engraving instruments) were used to inscribe materials such as wax and clay. From the Middle Ages, Metalpoint began to be employed for drawing. When the tip of the stylus was made of silver, the technique was known as Silverpoint. During the Renaissance, use of Silverpoint was frequent and many "Old Masters" such as Leonardo, Raphael, Durer, Holbein, Rembrandt, and Rubens made use of it in their sketches.