Where in Canberra is this survey plate?

Where in the Australian Capital Territory is this benchmark (BM) survey marker plate (general location say within 1 km)? Original post 20 November 2016, post updated 12 December 2016. Who’s into Geocaching, do you know the precise location? Clues: Space, STS, year 1981 and the number 26   🙂 Answer:  At the former Orroral Valley Tracking…