Public Domain icon. Closed circles can look like a border/restriction, as in trafficsigns.
So i made one with spaces in it.

Edit:
Worked with it a bit and changed it. It's looking somewhat stronger now. The other one was rather soft. Made it just black and white, so it can be used in several ways.

Tags: media, clip_art, public_domain, image, png, svg, icon, black, circle, copyright, icon, black, circle, copyright