The origin of this writing technology goes back many hundreds of years to a drawing method called Metalpoint. 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.
The pen is a modern version of Metalpoint containing an unspecified alloy. Unlike a pencil, the pen requires no sharpening and lasts a very long time. The writing result, however, seems to be somewhat light. Still, for about $30, as a backup marker or drawing tool that doesn’t, run, dry out, or need sharpening, and leaves a precise, permanent, fade- and smudge-proof mark, or simply as a novelty, it should prove a worthwhile buy.