under a microscope an original will ever look different as a fake; but to know the differences, you have to examine a lot of genuine specimens. Even coined fakes will show less detail than genuine ones. Cast medals will be recognized at the spot, because of all the gas bubbles and FAR less detail than genuine pieces.
no problem - it`s the socalled "tiger stripe" - variation. There was some error when producing the metal chips for the coining process; two different kinds of metal were fused, but not very well; you can see the one metal producing dark tiger-like stripes all over the medal due to it´s patina. I do like it very much somehow :)
I do use a Krüss optronic device, which unfortunately ran out of production some years ago. But there are newer generation ones of the same manufacturer (in Germany); also very good, of course.
Some more (quite crappy) images of a questionable partisan medal - nevertheless I would be glad, if I could get some opinions on this one.