File:Australian $50 note paper back.jpg

Summary
Source:

http://www.rba.gov.au/Museum/Displays/1960_1988_rba_and_reform_of_the_currency/inflation_and_the_note_issue.html

http://www.rba.gov.au/Museum/Displays/_Images/1960_1988/enviro_50_dollar_back_big.jpg