pushbutton incremental advance clutch with fixed sleeve
plastic barrel, metal components
I am unsure where this pencil fits in the history of micro-lead pencils, but it must be fairly early. It might be Pentel’s first pencil, does anyone know? Or maybe the Pentel Sharp 9 PS 100 is earlier. Fill me in if you know.
Notice the thin pushbutton. Only a single column of lead can be stored in the lead tube unlike virtually other every micro-thin pencil I can think of which all have a repository for a dozen or so extra leads.