Metal Detecting Norðmannaland

All finds treated with equal dignity, whether they be 1800s bag seals, or iron age brooches.
1) P154-S*-20-34 2) ??? 3) P-IXm1-143-39 4) P94-IVe1-7-39 5) P207-IXh1-22-38 6) ???

Shell casings of German make, found near an old military encampment east of Oslo. See caption for headstamps.

They all have a ring of notches around the near base, and we have yet to find out what they signify. Your suggestions are welcome!