Hi Adam.

In the days of communism, when Czechoslovakia was one, there were various factories making "Mauser" actions. CZ was one but there were several others. At that time all these actions were known as BRNO actions. In other words any action made in Czechoslovakia at that time was known as a BRNO action. It is probably a Czech acronym for "made in Czechoslovakia". There never was, nor indeed is there now, a BRNO factory.

ZBROJOVKA is the "real" name of the manufacturer, the BRNO suffix is just added to their name. It could as well be "CZ BRNO" or even "MARTIN BRNO".

I am certain this is correct as I used to have a "corner" of a business in Prague.

Martin