Dusky Antechinus (A. mimetes, formerly A. swainsonii). In the local area, this species has more evenly brown fur than the pale grey A. agilis or the grey and yellowish flavipes. Also shorter ears. But it is larger overall. A. flavipes is found in dry open forest and woodland at lower altitude. A. mimetes is in higher, wetter areas.
Hi Don, I was actually questioning your ID on this one until I learnt from Chris D that this is actually a typical juvenile Dusky. It lacks the longer front claws that might be used for species ID of an adult (that apparently develop as it ages), its ears seem a bit large in proportion to the head and higher set than typical (as head still maturing), and it has more white on the underbelly, again a youngster trait that makes confusion with A. agilis more likely. I just wanted to share these learnings!.
I’ll just add that scale can be somewhat inferred by the granite rock it is sitting on, and the typical crystal size of granite in Tidbinbilla. It was quite small in my uneducated opinion.