If it weren't for that hole, I'd say it is the letter "u" upside down on laser-printed paper... but does any macro technique would let you get THAT close to things?
3 Hints:
1. They are normally green.
2. When done professionally they are very semetrical (this one's home made)
3. Theres hundreds of them in an average home.
I'll drop another hint after my exam this evening. For now it's time for breakfast.