Lars, some years back you showed a cartridge by Eley with a name “Crown”.
Out of interest I came across this a few months back which I am fairly sure was manufactured by Eley-Kynoch but not sure of the exact date.
I have not seem this Head Stamp with the C- on a case before. The case does not give any clue to the company, it has a shield type logo similar to the Eley shield, and has written
Then in small capital letters douille importée literally translates to Imported Socket which I take to mean Imported Case. Being in French I therefor assume it was for a country that had French as it’s main language.
A). Did you ever find out anything more about your cartridge?
B). I wonder if there was any connection to your query?