Well, now managed to spend some quality time with the st.
It needed a thorough clean and it revealed some cool stuff. All the plastic is original, and date stamped 01/90, apart from the airbox cover which is dated 12/89. Everything on the bike is original, including the 28amp alternator and swing arm and engine. Also had time to look up the ownership history and guess what, it never was in Australia. It was part of the 155 "launch" bikes in 1990 allocated to australasia. Ie Australia and New Zealand. It was sold new right here in Dunedin NZ at McIvor and Veitch Honda. I am going there this week to see if they remember the bike and how they came to get it.
It may not be the first sold or the first registered, but it most definitely is the first off the production line for Australasia. Also a very early, and completely original going bike in world terms.
Will update more as it comes to hand.
Cheers