[codefox1]

Well, it was always 50 Hz when it eventually standardized (I understand when they first started the electrification there was no standard, and they used whatever, and there were DC mains, AC mains, 30V, 50V, 120V and such, and I suspect the frequency was not an issue - the main goal was the electric lighting).
Never really 60Hz, like it is here/

But, to tell you the truth, 220V is more convenient - you don't have to handle as much current, though it is deadlier, of course. But then to plug in an electric teapot that is 1 kWt of power, would take me to provide for a 4.5A wiring there and for 9A wiring here; there go your losses, flammability etc. (not that we had less fires that you do - probably more; Russians are notorious for their no giving a crap attitude when something goes bad, waiting for a disaster to happen, and they used aluminum wiring up until very recently, 80-s/90-s, whereas here it was outlawed way before, and people stopped using it even before that. And, what's worse, there are still places with it over there, as no one is required to replace it; just recently an acquaintance of mine from Moscow complained about two small fires one after another started in the outlets, and I told him that the wiring is probably aluminum and that was the reason, and he confirmed, that it was the case - the wiring there is aluminum. And all they did was replace the outlet, clean the wires and close it. There. )

As for the plug in Europe, I understand it is more or less standardized (one of my projects was a power supply that would work in there), or at least there is not as many varieties as there used to be.

The distance between the prongs is the same, but there is a GND plug, or GND ring, and most differences are still in the Eastern Europe where they had their own thing before 90s.

Russian plug used thinner prongs, and never had a safety GND, unless a specific plug was used (for heavy equipment, like electric washers, and then it was nothing like you've seen in appliances - flat prongs at 120 degree angles to each other), so it would fit a European outlet, but would be loose in it.

Also we used bare non-plated brass for the prongs.

The exposure is worldwide. That is not all recepticles are wired correctly even now. I think no assumptions should be made when working on sets, and they should all be fused. When in cabinets in reasonable environments with knobs on, etc... probably OK. Otherwise really dangerous. Beware!