1990 was one of the transitional years for Brno and/or CZ (technically, they're one and the same company).
From '88 to '92-'93, the firearms branch of the plant, Ceska zbrojovka (Czech Ordinance), was split off from the Cz Agrozet division (roughly Czech Ordinance and Agricultural works). Cz Agrozet was a foundry and machine shop that made parts for ag equipment and also some aviation engine parts. In the late 80s, the ag division was moved to other plants and just the firearms part of the business remained.
Around the same time this was happening, some of the models were changed and/or dropped since Cz was structuring more towards building forearms for the civilian market.
You can read a bit more at http://wwwczub.cz
, (or for a roughly translated english version of the story) http://cz-usa.com/about-cz-ub/
The Brno #2 is indeed the same rifle as the Cz 452. Most of not all parts should be interchangable.
I've heard that there might be fitting problems with using newer 452 mags in early #2/452 rifles...I believe I read that over at rimfirecentral.com, but I can't be 100% positive of that though since I've only seen one #2.