Most, if not all countries put serial numbers on their banknotes.
It helps to identify when and where they were printed, how many of them were printed and it makes counterfeiting just that little more difficult.
In more recent years, the serial number incorporates the year of printing, for example, a serial number of AA 06123456, indicates that the note was printed in 2006.
The Reserve Bank of Australia (RBA) and Commonwealth Scientific and Industrial Research Organisation (CSIRO) jointly developed polymer banknote technology.
The Reserve Bank of Australia advises that polymer notes last about four times longer than paper notes and are more difficult to counterfeit. Additionally, polymer notes can be recycled and are cheaper to produce.
Plastic (polymer)
the plastic Australian notes are made out of polymer
The original Australian paper Ten Dollar note (1966 to 1993) was 155 x 76 mm. The trial Australian polymer Bicentennial Ten Dollar note (1988 only) is 155 x 77.5 mm. The new Australian polymer Ten Dollar note (1993 to present) is 137 x 65 mm.
Have another look. The Queen is not on the Australian Ten Dollar note, only the polymer Five Dollar note issued since 1992. Prior to the issue of polymer notes, she appeared on the paper One Dollar note issued from 1966.
The Australian Five Dollar note was the first polymer banknote to be released into circulation completely replacing the paper predecessor, and was the first polymer banknote to be successfully integrated into the currency in the world. It also has an impressive list of security features and gadgets to foil counterfeiting.
Since 1992, Australian notes have been printed on polymer film by Note Printing Australia. This subsidiary of the Reserve Bank of Australia is located in Cragieburn, Melbourne. This same facility also prints New Zealand's bank notes, also on polymer.
Australian banknotes are all made of plastic, specifically polymer. Australia was the first country in the world to have all its banknotes made of polymer. The composition of the 5, 10, 20 and 50 cent coins is 25% nickel and 75% copper. The $1 and $2 coins are composed of 92 % copper, 6 % aluminum and 2 % nickel.
The character on the holographic window of the Australian One Hundred Dollar note is a "Lyre Bird". These are part of the security devices included on all current Australian polymer banknotes.
Both old and new Parliament Houses appear on the Australian polymer Five Dollar notes as a symbol of our democratic system of government.
To reduce the chance of counterfeit notes and also to make the notes last longer.
The new polymer notes are mostly blue but have swirls of yellow and green as well.
The Reserve Bank of Australia does not give out that sort of information as a safe guard against potential counterfeiting. They only go so far as to describe it as a "polymer (plastic) substrate".