I wonder if this uses a low melting point alloy like Field’s metal.
The solid metal ‘nib’ consists of a metal alloy, that leaves a mark on most types of paper. If you use the sort of paper typically used in printers and photocopiers, the pen leaves a mark that looks as if it was made by a pencil. However the line will not smudge, and cannot be rubbed out. Since there is no ink, there is nothing to dry out, so the pen will work just as well in 25 years time as it does today. And of course it never needs sharpening.