I agree, it doesn't seem to be anything besides a normal $10 bill that picked up some color one way or another. Keep an eye out! You are bound to find something cool eventually.
Something from being in circulation gave it the added color but it has a cool look. I would save it just for fun.
Seriously? It was just exposed to something that caused it to pick up the color. Think about how it could have gotten that way before leaving BEP. It was probably in a leather wallet that got wet.