There isn't actually an abandoned mine here, just an abandoned mining machine...
The first thing I thought of when seeing this, back in 2016 on our first real geocaching road trip, was that it looked like a monster, a bit like something Mr and Mrs Incredible would need to fight! Of course we stopped here to find a cache hidden within the monster, one reported missing and archived a while back now.
As the sign says, it is a Lee Norse continuous coal mining machine, dating back to 1959. It's an impressive piece of hardware, built a bit like a tank. It is located in Jim Johnstone Reserve, easy to access for all sized vehicle off the Golden Highway, and even has facilities.
The cache is magnetic, about the same size as a small sistema, 200mL or so, hidden so other reserve users shouldn't see you looking....