Which country is this?

It's almost forgotten now, but, in the manner of Bombay—>Mumbai, in the middle of the 20th Century, one well-known Western European state recurrently tried to persuade Anglophones to call it by a name almost unknown in English. I recall that many maps and globes I saw as a child in the 1960s used this obscure term as the main name for this country, with its famous English name in smaller type in parentheses below.

My cousins were attending school in this country when I visited them in 1965. They complained about having to take classes in the indigenous tongue, saying that English was the language of the future. Whiny snot-nosed teens they may have been, but they were right.

Got it by now?

Emphasizing the local name over the celebrated English name was an anti-English-colonialist gesture, same as changing Bombay to Mumbai (with, same as in India, the added bonus of pleasing some locals and displeasing others). But in this case, it didn't stick because it was too confusing and too inconvenient for foreigners, so the locals have largely given up on the name change, just as they have largely given upon the language. To this day, only this indigenous name appears on postage stamps, but the American media have largely given up using the new name and gone back to the more familiar old name.

Wikipedia gives an example of common-sense prevailing in this country:

From 1938 to 1962 the international plate on Irish cars was marked "EIR", short for ?‰ire.^{[citation needed]} In 1922-1938 it was "SE", and from 1962 "IRL" has been adopted. Irish politician, Bernard Commons TD suggested to the D??il in 1950 that the government examine "the tourist identification plate bearing the letters EIR" "with a view to the adoption of identification letters more readily associated with this country by foreigners".^[4] The amendment was effected under the Road Traffic Act 1961.

So, the lesson appears to be, once again, that non-Europeans get to change what Anglophones in the West call their historic places, but Europeans don't.

By the way, this is a different situation from the country on the opposite side of England insisting upon being called The Netherlands rather than the traditional Holland. Holland refers only to the culturally dominant coastal stretch that contains the big cities, but only 13% of the land area. It's the analog of using England to refer to Great Britain or the United Kingdom. It makes sense to choose a new name when incorporating a larger region or shrinking (e.g., Montenegro).

But, today, the main examples of European countries getting to change their placenames, following the dropping of some dictators' names at the end of the Cold War, is that Ukraine has talked the media into not referring to it as The Ukraine.