I was reading a bit about Zimmerit. The Germans created a magnetic anti-tank mine and were worried that the allies would copy it so the started coating their armor in Zimmerit which reduced the ability of a magnet to stick.
Last line of the article I read is kinda ironic:
Another reason for discontinuing the expensive and time consuming process was that in the end none of the Allied nations used magnetic anti-tank mines, so it was a wasted effort.
It's those Germans making work for modelers again
