Translation: “silver look” / meaning: a slight squint
It sounds like it’s a special power of a rightly forgotten Marvel comic hero from the late 60s. In reality, however, bearers of a Silberblick can neither search for treasures nor turn their fellow humans into precious metal.
The word refers to a slight squint that, depending on the beholder’s preferences, may well be considered to be kind of sexy and mysterious. In art, the Silberblick is even deliberately used as a painting technique. Just think of the 500 years lasting fuss about the Mona Lisa (no, she does not follow you with her eyes, you are pretty but not that pretty). According to a popular theory, the term goes back to the peculiar shimmering of silver at the end of the melting process. This is said to resemble being looked at by two slightly displaced pupils. However, one can only speculate about the truth of this derivation.
Definitely not true is the threat of German parents that you should not squint intentionally, because otherwise your eyes will stay in this position. This is about as accurate as the story that masturbation makes you blind.