As with most mystery caches the cache is not at the listed coordinates. They are for the Gunning Court House which was built in 1879.
To calculate the GZ coordinates for this cache you will first need to compleate the Great Southern Road Breadalbane to Gunning Adventure Lab.
There is also an AL bonus cache in Breadalbane that can be solved by doing the same AL cache.
https://labs.geocaching.com/goto/GSR
GZ is at S34 FH.AAI, E149 AF.EAG