Guardian $25 Polymer Test/Promotional Note - Indigenous AustralianGuardian $25 polymer test promotional note. Guardian, the proprietary polymer substrate, is a trailblazer in the world of banknote printing, employed by over 30 central banks globally. This advanced material was developed in collaboration with CSIRO, the University of Melbourne, and the Reserve Bank of Australia. The inaugural polymer note, the Johnston Fraser Bicentenary Ten Dollars, was issued in 1988.