Even if the title might seem self-explanatory, I would ask you to read the entire post to understand what exactly I'm trying to understand here.
I'm from the Russian Federation. We don't have a lot of departments of pure mathematics. Most of those undergraduate programs named "mathematics" are actually aimed at people who wish to teach mathematics to engineers/IT/finance people or those who themselves wish to get into engineering, IT or finance. Actually, when I say "we don't have a lot" I mean we have two and a half. No exaggeration here. My explanation is actually a bit oversimplified, but I hope you understand what I meant to say.
The funny thing is that the most renowned of Russian schools for the quality of its pure mathematics students is called Independent University of Moscow. They offer free education with entrance based on how you perform during the process of education itself. It has no entrance exams, everyone can attend lectures at first, but to get the status of a "student" you must do well in a first three mandatory courses. Why did I call the situation a "funny thing"? The reason is that its degree is not recognized as an official undergraduate degree in Russian Federation. So, despite being called Independent University of Moscow, it doesn't have an official university status in Russia !
What I wish to understand is how top graduate schools in mathematics would treat a candidate with such a degree. From what I understand, it has a good reputation in mathematics. Many people from IUM were accepted to the best graduate schools in mathematics all over the world. For example, Harvard, MIT. Some of those even had their IUM "degree" as the their only degree. That is, they didn't have any official Russian undergraduate degree in any field.
But IUM doesn't have a lot of alumni. So, those IUM alumni attending MIT/Harvard might look like special cases, even exceptions. Besides, all recent IUM graduates had another official degree from another Russian university. The latest case I know of with a man being accepted to MIT with only an IUM degree is dated 2006. Moreover, even if such a practice was appropriate in US before, it might have changed in recent years, I'm not sure.
That said, I understand there were exceptional cases of enrollees being admitted to top graduate school (in US) without any degree at all, based on their exceptional recommendations or their research. I know at least three such people, all from my country. They applied in 1980s/1990s to Harvard and MIT.
So what I'm trying to understand is how do graduate schools treat the lack of an official status of a foreign school with it being a strong academy with capable students and top-rank professors. Another nuance I'm thinking is that, from a US/Can/EU university point of view, it is an overseas school. I'm not even sure how to US departments verify the validity of one's undergraduate/masters degree if it's not from US or EU.
Of course, what I'm asking is purely about bureaucratic procedures within academia. I absolutely understand that to have a chance in getting into top graduate school in mathematics you must have exceptional credentials: recommendations from renowned professors or even your own research articles. But, say, one has such distinctions (for example, you can get those things during a successful process of getting a "degree" at IUM, that's the reason it has so few alumni). Yet how would top overseas graduate schools treat such a potentially strong candidate if his degree is not official in the country where it was obtained ?