CZ has always mfgr. the rifles with whichever brand name(Brno & CZ). The Brno ZKK-600 series is now discontinued and is now replaced by the CZ 550 series. The basic mechanism in both rifle are almost similar(certain parts can be cannibalised from one to the other).
Older Brno's at one point had a flip up emergency peep-sight, an already very good express rear sight has always been available.
The newer CZ-550 Magnum also has exactly the same type of express rear sight (but unluckely no peep-up rear sight)
Both brandname have mostly been mfgr. with steel component, basic quality thru & thru.
Have a look at CZ-UB(Czech Republic) e-site, there's a lot of info. within the site but you have to take the time to check info. out.
Hope this reply helped you.
All the best,