Steel cased double culot rimfire

Here is a 6mm/22 Double Culot I picked up at SLICS. I appears pretty normal except the base is brass plated steel rather than the normal solid brass (attracted to a magnet). Are there any other steel based double Culots cartridges? Also any idea when this was manufactured?
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Thanks,

Paul

I think, this .22 Double Culot (not 6mm) was made by NCS, France
but I am away from my books…
PP

yes you are right, NCS is for Nouvelle Cartoucherie de Survillier.
Normally branded “Concorde”.

Thanks guys

Any idea when NCS was in business? Also any guesses when this cartridge was manufactured?

Paul