This is a Merz & Krell piston fill pen in blue cell/brickwork celluloid from the 1950s, an unusual celluloid pattern. It has a large ink view window in the barrel with a black and clear spiral pattern with enough clarity to see through the window, giving a criss cross effect. The piston knob is accessed by removing the black end cap. The nib is a lightly gold plated Number 2 stainless steel semi flex and some of the plating is still intact. There are no makers marks on the 4 13/16 inch long pen other than a half eclipsed sun stamping on the nib.