bxn is a Czech Designation for a certain production factory. bxn is for Sellier & Bellot. Prague, Czechoslovakia. Factory in Zbrojovka Vlàsim,
The Czechs carried over the unique German Third Reich era tradition of using mostly 3 letter codes to denote which factory a certain arm or munition, etc, was made... Makes sense as the Germans had 2 large factories producing arms for them in occupied Czechoslovakia, which when the war ended, kept producing arms for the new Czech Post War State, and for export.
Very cool . I love this kind of history !