Each ink stick of a set of ink sticks for a phase change ink jet printer has formed on the top of the ink stick a three dimensional visually recognizable symbol. At least a portion of the visually recognizable symbol on each of the ink sticks is different, so that the printer user can distinguish which...http://www.google.de/patents/US7063412?utm_source=gb-gplus-sharePatent US7063412 - Visible identification of solid ink stick
