peut être ouvert d’office, peut être?

I saw this on an envelope the other day. What can it mean?

To me, it clearly means “May be inspected only by two-dimensional officials with the Eye of Horus wearing a cap at 30° bearing insignia of an upturned army helmet with a lion rampant and a blancmange.”

Oh, and this is my first post with SVG graphics. Yay!