A method for selectively indicating a changeable characteristic of an article or of the contents of a container includes use of mnemonic device comprising a body having a plurality of predefined indicator marks placed thereon, and a means associated with each one of the indicator marks by which...http://www.google.de/patents/US5706948?utm_source=gb-gplus-sharePatent US5706948 - Method for identifying a characteristic of an object or contents of a container 
