My thanks to Marconi too, this is often the sort of thread that I get deeply stuck into but having been ill I haven't been around much, so I am pleased he was able to help in detail.
The original timer is interesting but not 1950s. The components suggest early late 60s / early 70s. The active guts including probably a couple of transistors are inside the flat grey module between the power transformer and the relay. The transformer powers the module and relay coil via the red BY123 bridge rectifier and smoothing capacitor (the smaller of the two electrolytics). The RC timing circuit probably comprises the 100μF electrolytic, the control pot, the 2.2kΩ resistor and the full-scale setting preset. The set of relay contacts nearest the module are tied into the timing circuit, I can't see in what way, either to provide hysteresis or a discharge path.
If the Japanese-made Rubycon electrolytic is original it is a hint at the location where the timer was assembled. The other electrolytic, 2.2kΩ resistor and possibly the rectifier are Philips parts made in the Netherlands. It's unusual to see Asian and European capacitors side-by-side in the same device in Asia or Europe, but much more likely that a manufacturer in NZ or Aus would buy parts from both continents as suited their requirements. I wonder who made the grey module? Any ID on it?