Had this charger for a while. I know almost nothing about Eastern Block ammunition. It is loaded with 10 steel dummy cartridges headstamped 05 68. I believe 05 is Spreewerke, Lübben, East Germany. do they go with this charger ( is BXN East German)?
I am not familiar enough with the Warsaw Pact supplies system to say that your charger could not be one that would have been used with cartridges from the DDR, but I can say that “bxn” is the code for the Czech ammunition factory Sellier & Bellot. It is quite possible that they made stripper clips as well as ammunition, and perhaps other items as well.
Your identification of the cartridges is correct - they are East German. I would not, for collecting purposes, consider the cartridges and the clip to be a match.
One caveat to my opinion. I have had dozens of SkS stripper clips go thru my hands and don’t recall ever having one with 04, 05 or any other code I could identify with the DDR. If it turns out they didn’t make any SkS stripper clips, then they could well have gotten supplies of them from any Warsaw Pact country that did produce them.