I am very sorry Banquo, but these nuts do not say anything to me. This time, I am sure that Maestro Grossman will be the man for a genuine expertise. They are not made by SMC.
Steve, I am not sure that the Grivel stacking nut was ever marketed, one more reason to make it so hard to find. The same week I received it from Denis Pivot, there was one sample on eBay.com. It was just incredible, as I had never seen such a nut on eBay before.
I too saw the Laprade Coinceurs Gigogne on eBay recently.