first - personally I'm sure that the Totenkopfringe were cast. The detailed pictures speak for themselves.
Attached is a picture of my 1941 ring, brought out of the ground by myself in 2008. Unfortunately you can see a slight damage by my folding spade at this exact spot, but guaranteed original. Sorry, my camera is over 20 years old...
Could your Africa ring also be (in German) tauschiert? I can't find the right word in English (maybe damascening?), but I mean this:
https://de.wikipedia.org/wiki/Tauschierung
Would also fit the origin North Africa, I believe.
At this point thanks for all the effort, I'm curious the further course of this discussion.
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