A frequent Agaricus that we find in both Pinus radiata and native forest in the southern Dandenongs, is a large, scaled cap species with brownish to purplish colouring, white to grey gills that turn chocolate brown with age, a thick stipe that can be spindle shaped, meaty and often worm-ridden. The largest specimen here was 19cms in diameter so quite large.
Importantly the flesh does NOT stain when damaged, scratched or cut and while it appears to be an edible Agaricus species myself and others have found the flavour to be bland or poor.
So we got it sequenced (ITS) and through BLASTn it sits about 1% away from 2 sequences for Agaricus subrutilescens, at also sits very close to Agaricus impudicus and two Australian species with sequences designated JF495039 and JF495040.
Macroscopically this mushroom appears identical to many online photos of Agaricus subrutilescens.