The 7.92 cartridge case was covered with purple paint. Is this an experimental case which used by German infantry in training？
Can you post a picture of the whole cartridges? As far as I know, the Germans had no purple cartridges. Only green ones , the Nahpatrone. This could be home made cooking or maybe some rework by some non-german authority?
A smk-H cartridge？I guess
Alas, some home made fantasy I presume. According the lotnumbers , the hlb case was loaded with an SmK bullet (AP), the asb was an SmK L’spur (AP-tracer) and the P94 was an sS (heavy ball). This also corresponds to their primer annulus colour, still visible.
Were these cases put on an ink pad maybe?
See that frequently with turn-in ammunition. Reloaders marking specific loadings most frequently, but also when some shooters move ammo out of the original boxes and identify whatever is important to them - date of manufacture, loadings, etc…