I was looking at this coin. And I read Yiefs, as I got from left to right (Yes/if)
https://sma.nasa.gov/sma-disciplines/safety-culture#Yes_If
That´s what I got from searching yiefs
https://www.nrc.gov/docs/ML1034/ML103420327.pdf
I have no idea what I have read there. Something with nuclear… Maybe I am too stoned…