What year is the car?
The multiple VIN locations might be year dependent, but I can't remember what year that started. My 73 has the VIN at the A post, the plate on the door post and stamped into the radiator support.
With your VIN missing from these locations I would suspect it had been stolen. Common thing, steal a car from say the US, remove the VINs and ship the car to South America for resale (usually the luxury rides and SUV's). Could be a similar situation with yours, stolen from Europe and shipped to Australia. Did you get a title when you bought it, or was it yours at the time it was stripped of it's VIN's?
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.