Please remember Australian Standards have changed over the decades since all these items were manufactured. These products may not meet current Australian Standards and are sold as a memory from the past.
 
Metal door handle 
 
 
 
This is a vintage or antique door handle set backplate and pull knocker, possibly from the interwar period (1920s-1930s) or Californian Bungalow era. 
It is a surface-mounted style, made of metal with a painted finish that shows significant wear and patina.
The large circular cutout at the top is for a doorknob/lock, while the smaller holes at the bottom are for mounting screws.
The integrated pull handle is a common design for that era of domestic architecture in places like Australia and the UK.
This backplate measures 20.3cm x 5.3cm.  The handle measures 12.5cm x 1.8cm, with a surface projection of 3cm.
It is in good condition. Please study the photos.