Nice image. Yes, an M60A1 (modified), one of the two provided by the US DOD for the Medium Tank Trials against the German Leopard 1A1 (modified) in the 1970s. Trials were at Puckapunyal and in Queensland, both coastal (Tully) and inland.
The choosing of vehicle types for the trials, the trails, and the decision process that ended in purchasing Leopard are all covered in detail in my 2015 book 'Leopard AS1 in Australian Service' published by Trackpad Publishing in the UK.
www.trackpadpublishing.comMike