This is certainly a replica, made by Willem van der Eng a Dutch Collector. He has made a number of replicas, mostly of very rare experimental German cartridges.
The headstamp was a capital R in circle or the word copy on 12hrs and on 6nhrs ern or er.
The meaning of ern: Eng Reuver Nederland and er: Eng Reuver.
Regards,
DerkJan
[
Draco dormiens nunquam titillandus
lo spirito di Cesare, vagante in cerca di vendetta, con al suo fianco Ate uscita dall'inferno, entro questi confini con voce di monarca griderà "Sterminio", e scioglierà i mastini della guerra
