Picked up 3 lots of common medals and awards from a collectors sale.
This lot had I.D tags, Erkennungsmarken.
These are my first ones and I have no idea how to read them.
Can someone please if its a zinc or aluminium tag?
Should I clean it?
Is there a way to trace the old owners units movements?
Lastly, could someone please translate the disc for me?

Cheers,