File:No Zlo Shroomsky.svg

Summary
I'm the copyright holder, this thing is Proprietary. It can be used here.

 :) 

This is the No Zlo Shroomsky seal used on government documents to prevent the Professor from declassifying an item. The square and lines behind the no symbol is actually what I originally drew as a "mushroom", long before and circa 1999. It was a short while later that I started to use the familiar oval and rectangle you see today.