Required in many counties. It has the locations of all the switches, PWs, etc.
What did you think of the font they used on the placard? Very unusual, but I guess that is the point.
BTW, your inspection sounds like mine. Did they make you sign something that said you had smoke and CO detectors in the house?
I have the placard as well with the location of panels, disconnects and powerwalls. I did also sign a document that said I had smoke and CO detectors in every room of the house.