I do remember these, too.
Inherited some of these from my father, who had acquired them sometime in the 1970s.
Intended for reforming into 11,2x51R Kropatschek-Heissig.

These cases have very thin walls and little material in the case head area.
Good case volume for loading black powder but very susceptible to case head separation.

The case shoulder needs to be just in the right position, or you have split cases.
fuhrmann