I'll have to leave it to one of the Victa guys - in particular Joe Carroll, but there are some others too who know them all - to identify it. You said it is self-propelled, and that cuts the number of possibilities way down.
Bear in mind that not all of the interior of the carburetor is subject to vacuum, so not much air leaks in through most of the apertures, and the wire should be a decent fit in the kill switch grommets (two wires have to enter separately, and joining them together kills the ignition).
Air filters are very important on mowers, because the engines operate close to the ground, and sometimes (especially in Australia) that ground is dry and the dust rises when the mower blades fan it vigorously to make the cut grass lift up into the catcher. Your particular mower has a snorkel air intake so that the air it draws in is taken from a couple of feet above ground level, and this helps a lot compared with air filters mounted directly on the carburetor. Nevertheless it needs an air filter, it just won't have to be changed very often. (The snorkel-type filter element in my own mower has "2005" written on it by hand. It was in the mower when I bought it second-hand. It looks perfectly clean to the naked eye, but it wouldn't be if you examined it closely. In the British climate yours may last equally long: just take a look at it once in a while, and when it gets seriously dirty, replace it.)
