Coin rings – how were these made?

Ed writes –

Phil, For years I have been making coin rings using the traditional method of tapping the rim of a coin until it’s flat, drilling out the center, filing etc.. Recently I came across some coin rings that appear to be made using an alternate method and possibly specialized equipment. I’ve searched the web and I haven’t been able to find any info on technique or tools used to make these rings. Could you please ask the readers of Makezine blog if they have any knowledge of how these are made and what tools might have been used to make them.

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