The coin filler is a variant of the previous match-stick filler system in which instead of a match the user pushes directly on the pressure bar using a coin or a medal or similar object, often elliptical in shape to allow a smaller width of the slot made on the pen body. Also in this case, in fact, the pressure is exerted through a lateral opening made on the barrel of the pen.
The drawbacks are substantially the same of the match-stick filler, soothed from the fact that a coin is an object generally more common, and it is not necessary to be a smoker. The larger size of the slit on the body, however, made the pen less elegant and more prone to problems. Often the slit is identifiable with respect to the case of a toggle pen in which the latter has been lost, by the presence of an additional round central hole slightly larger than those of the slit.
The system was used by Waterman in some models between 1913 and 1914, which were sold with a special coin. The scarce practicality of the system led to the disposal in less than a year, which makes these pens (that sometimes can be confused with later models with lever, but missing the same) rather rare. But even rarer and much sought after by collectors, are the coins supplied with the pen, since most of them were lost.