A mystery Parkette

Periodically someone asks about a mystery pen on the pen forums: a 1930s Parkette that is a lever-filler but also -- seemingly -- a button-filler, with a hole in the end of the barrel covered by a screw-off blind cap. It's not so odd or mysterious, however, as the picture above will make clear. The pen is an ordinary Parker Parkette, adapted so it can do double duty as a pocket pen or desk pen. Usually the parts of the ensemble have been scattered, so the purpose of the blind cap isn't obvious. The central hole, incidentally, is there because Parker made these pens from celluloid tube stock, which was cheaper and faster to cure than solid rod (a solid plug certainly could have been used, as Parker did for the cap tops and the barrel ends of non-convertible Parkettes, but this was an economy pen, made in the depths of the Great Depression).