Cadpat Toxicological overalls featuring the same breast and leg cargo pockets as per the combat uniform, in addition to a zippered pocket on each upper arm.
A google search turned up a good article on the uniform, ironically enough, from the Australian Army newspaper.
Detail showing the subdued national insignia, zippered sleeve pocket and (presumably) patch for the toxic indicator swabs. Not sure why the national insignia is on an attached velcro tab.
Detail of the interior showing two way brass zipper and rip-stop lining made of same material as the indicator patches. Note also the existence of internal braces and straps which were cut off by the previous user.
Detail showing leg zipper opening. There was also existence of a strap for securing the ankle which was also cut off in this case.
Googled the NSN which indicated the item to be a toxicological suit.
Unlike most CBRND/NBC suits I am aware of this is designed to be re-used at least 5 times. It is substantially better quality and could almost double as a cold weather piece.