Following the thread of finding fired cases, I thought this might be of interest.
After Britain had adopted the modified Czech Zb26 as the Bren gun in the mid 1930s, it was decided to test the Zb53 with a view to converting it to .303" as a possible replacement for the Vickers in the MMG role. With war approaching it was decided this would be unwise and so the Zb53 was adopted virtually unchanged in its original 7.92mm calibre as the BESA tank machine gun. The records show that the ammunition used in the tests was Czech made 7.92 headstamped “19/Z/36/XI/”
Back in the 1980s I was shooting on one of the test ranges at the Royal Small Arms Factory at Enfield and picked up a very dirty fired 7.92 case that was half buried… and there it was, exactly the right headstamp from the trials, complete with the classic oval firing pin strike.