Yes Morrison is correct ,I just call them Masport as Masport took over Morrison in 1986
I've got a couple bases the same one branded Scott Bonnar but both Morrison
I don't think it would be late fifties., my Scott Bonnar has the same wheels.
It does look like your motor was changed or just the cowl but wheels look later than fifties on your mower.
1960s-1970s: As global mower manufacturers started to innovate, cross-tread tires began to appear more widely by the late 1960s and early 1970s, both in the U.S. and in Australia. This was driven by improvements in traction, durability, and maneuverability for mowers.
So, while cross-tread tires appeared a bit earlier in the U.S., they likely became common in Australia by the late 1960s as well, though not necessarily across all brands or models immediately. There would have been a mix of straight-tread and cross-tread models during the transition period.
