Mobilco Heavycut slasher. Looks to be the 'Standard' model, with the big spoked wheels - in the '70's there was also a small disc wheeled model, called the 'Estate'.
Not too sure of the year, but if the original paint colour was yellow, it'd be pre-1977 for sure.
Dunno how original the blade cover is, though - I've only seen round ones.
Like this one pinched from a recent FleaBay ad:
Some of these only had a skid on one side of the deck, some had the half skid on the LHS as well.
Some parts are still available from Heavycut Machinery, who took over manufacture after Mobilco Limited [a farm/garden machinery importer and manufacturer located in Mitcham, Vic] was shut down in 1976-7. They will do restorations on these machines too. Dunno about parts lists or manuals.
http://www.heavycut.com.au/index.htm