What a great research work! Thank you, Vasco, for sharing this interesting information.
I do also have a similar pen, Pelikan 100N EMEGE, and can confirm some of the characteristics you mentioned: piston shaft, cork locking mechanism. I repaired my pen some years ago (replacement of the cork) and since then is running (writing) without problems.
The pen belonged to a relative and unfortunately I do not have any further info about his history.