I have seen blue fibres on $5 and $10 but not on a $20. There is printing on top of the fibre so I am assuming that it is not something that got stuck afterwords.
It make nice little arrow sign on the wall of the building. The image below shows the context and an enlargement of the fibre.
Anyone seen such a fibre? Any thoughts?
{http://img832.imageshack.us/img832/5542/fibrearrowfronte.jpg:http://img832.imageshack.us/img832/5542/fibrearrowfronte.th.jpg}
