Playing with metal blanks. These are ferrous coins with a plating.
Made on a 20w fiber. I am playing with getting different textures and shades by altering the frequency. I am also experimenting with burn order, which has a seemingly bigger impact on a fiber than co2/diode.
They look like they have a thin brass layer that covers a blank of some other metal. That isn’t a bad thing. Once you got your settings right so that you etched the brass off without overdoing it…but, if a magnet attracts the coin my guess is that it won’t be that durable. There will be corrosion as the steel rusts.
As to why the magnet attracts the aluminum ones, maybe they are permanently spinning over the misdiscription.
Worst part, though, is that the coin blanks on Amazon are so dear.