G'day Widget,
That mower most resembles a Model 506, 1962-3 Ambassador. But it could be slightly bitserised - it has had a repaint, after all.
For sure, the engine is 1963 or earlier, as it has a Zenith carby. Victa dropped those from late 1963 onwards, and used only Walbro carbs on their Kirby-Lauson 4-stroke models thereafter. That engine would be either an LV30 or VK30 125cc, to use the engine manufacturer's model designations.
However, the chassis looks more like a 1964-6 Corvette 4 Model 524, with that LHS side discharge. The 506 has that on the RHS, in the Victa green book line drawings at any rate.
