Well, on my last trip thru FRA, at the F terminal, the screener asked me about "the metal balls" in my bag. I had no idea what he was talking about, but he showed me the image of something that looked sort of like the image of an egg carton with 8 or 10 round thing. I was quite embarrassed and worried. I opened my bag and saw that I had a cardboard box of collectable German coins (have a subscription but don't even open them anymore) on top.

With relief I told him they were coins. I didn't have to open the package.