I wonder if this is a Knock Down kit car, I am almost certain (please confirm ADRIAN) This is not an Australian car, Knock down kits had additional letters added to the chassis numbers to denote the state in which the car was assembled:
South Australia. = A
Queensland = B
Victoria = M
Western Australia = P
New South Wales = S
The "N" may well be for New Zealand or for Knock Down (either way it needs to be confirmed) if it is NZ then here is the birth place of your Car: