The Pelikan M205 Duo is known as a concept and quite usable for marking purposes. Anyone who already owns several M200 models can fall back on alternative luminous inks, e.g. the Namiki Pilot fuyu-gaki mandarin ink. Special marker inks from the ink booklets by Michael Richter (available on Penexchange and Fountainpennetwork) are also an option. Thus it can be prevented that other valuable fountain pens have to be loaded with aggressive marker ink.