Kennedy Disapp Ink
John Kennedy and Ken Rosenthal present two effects with thus unusual pen.
1- SPLAT! – The magician causes a portion of the pen’s ink cartridge to splatter onto a white card. The mechanism still moves up and down even though the cartridge is no longer in the center to support it.
2.- DISAPPEARING INK- You create an optical illusion by making a black ink cartridge “disappear” against a black card. The illusion becomes real, thigh when you move the card away and the ink and cartridge are really gone! Not only that but the pen mechanism still moves up and down with no center support.
A few dozen are in stock although this has been discontinued. Use a standard replacement