The 9120a printer that sits on top of a 9100 calculator seems to be the electrostatic type: that is, the printhead electrically vaporizes a thin coating on the paper's surface to expose a black layer underneath.
I recall these printers from the 70s, but it's been decades since I've seen one or the special paper they use.
Are there still any sources for this paper?
Edited: 7 Nov 2011, 11:01 a.m.