Ewan

Regarding your last question, early Brno ZKK 600/601/602 had a really neat integral pop up rear peep sight as well as a fold-up conventional rear sight.

Pre '68 Brno ZKK's had a lock screw and engraved reference marks on the peep's windage, later ZKK's had dropped the screw... then the rear peep was dropped altogether as a cost save by the 1990's.

I think they are a really great feature that CZ should reintroduce!

Cheers

TM