I tried to provide you a stamp company's link for further information on this stamp, but it was blacklisted from this site because of excess spam. So I've cut and pasted their description of the stamp, which may be of some help:
Quote:
"The stamps were 100% official issues by the Federal Government. They were approved and sold at face value by the Australian National Parks and Wildlife Service, which changed its name in 1993 to the Australian Nature Conservation Agency. Both governed by the National Parks and Wildlife Conservation Act of 1975. Monies from their sale went to Federal Government consolidated revenue.
These beautifully printed large sized stamps were primarily issued to receipt the entry fees to Wetland Parks, most notably the famous World Heritage Site - the Kakadu Wetlands in the Northern Territory. These stamps were used on entry tickets to the Kakadu Park. All visitors needed to pay a $15 entry fee to the Park at this time, and the entry ticket was receipted with a cancelled copy of this stamp being affixed.
• The 1995 $15 issue depicts Australia's Green Pygmy Goose. Designed by Robin Hill.
• The 1996 $15 issue depicts Australia's Blue-Billed Duck. Designed by Richard Clifton.
The stamps have been popular worldwide with not only collectors of Australian stamps, but worldwide collectors of "Bird" and "Duck" stamp thematics."