Exactly how much is "one glass", in Russian recipes?

In many many Russian recipes, measurements call for one glass or this one glass of that.

One glass in Russia, appears to be a similar concept to what one cup is in United States.

But here lies a problem, I will run down the list:

• USSR mass-produced a certain type of faceted glass that pretty much everyone had in Russia. The facets on the glass ended before reaching the top of the glass, thus marking a natural edge.
  
  
  
  
  • Pouring water into glass up to that edge == 200 milliliters
  
  
  • Pouring water till the top of the glass = 250 milliliters
  
  
  
  

It is NEVER specified if you are to fill up till the edge or to the top.

Now Russia produces all kinds of "glasses". Looking around Russian native sites, I see that one glass can be anywhere from 180g, 200g, 250g. Also, measuring water, sugar, and flour by volume this way, will produce different weight.

Does anyone have an experience in this?

I have a recipe that calls for "approximately 4 glasses of flour". How much do I put?

I suppose I can use "one US cup" measure, but I know that one US cup, as a measurement vessel/quantity, did not exist in the recipe originator's minds in Soviet Russia.

Question: how much is 1 glass? Is it safe to use one cup?