Pete, Kirby made the Lauson engine in Australia, initially branded "Kirby Lauson" and later "Tecumseh" (the American conglomerate that owned Lauson). They made 2.5 and 3 hp versions in the early days: the ones with horizontal crankshaft were called HK25 and HK30, while the VK30 was a 3 hp engine with a vertical crankshaft. Because the Lauson was made in Australia and the Briggs and Stratton was not, most Australian lawnmowers with 4 stroke engines had Kirby-Lausons from the late 1960s until the early 1970s. It was not a nice engine to operate in my experience, but they were quite durable mechanically.
I don't recognise the mower frame, but someone else probably will.
