Extremely nice finds !
It looks like one of the cartridge cases does not have a bottom/rim - true ? If yes, these are often produced this way or made with the purpose of training MG personnel. In the training an instructor load it in a chamber and the MG team should learn to clean / empty the chamber with the universal tool.
Even today in the Danish army you have a training kit containing cartridge cases with different types of damages for training the MG-3 (MG-42)