hi, the square dark area is concentrated but the entire obverse is darker that a normal bill, if it were sitting on something the stain would have seeped thru to the reverse. I did not add a normal $5 bill for comoparison. its hard to tell just from looking at a picture to truly see the difference. I will upload comparison pics. this bill is Gem Uncirculated. anything is possible. I got it from brick of bills.