I could almost be tempted to see a darker colour behind the last four digits so maybe the entire number is a Polish replacement.
I doubt that an ex Polish machine would turn up in Australia in 1942, and if it did the original number had already been lost so they couldn't have noted it in the Australian ledger.
Its also possible that the machine has been retro fitted with a side damper knob, so maybe "if" the last four digits are original then it could be earlier, 4199789 or 4349789 perhaps?
In 1940/41 the Dutch free forces also started with C128xxxx numbers.
Later pictures show that these numbers were replaced by the more "usual" ranges.
Neither the Nortons nor the BSA's had Census numbers with any relation to the mating frame/engine numbers.
Totally random.
