[tdeck]

There was a Cyrillic code page (remember code pages?) designed so that most letters would be at the same code point as corresponding Latin letters, just with the high bit set:

https://en.m.wikipedia.org/wiki/KOI8-R

[bonzini]

And with uppercase and lowercase exchanged!

There was such a font too, it was called Czar. I used it in Windows 95/98.