What do you think, printing error. Should i keep?

I have a US 1 dollar bill that looks like it has finger prints on it. Would this be an error, or just an oddity.
on front

on the back you can see the ridges.


my images do not to it justices. Is it a keeper, or should I let it go.
could it be a fake? I do not think so
your thoughts thank you daryl

Could it be post-printing error? Looks like someone at the bank was counting it with a dirty thumb.
But it is from the printer that way, cool.

The ridges on the back are from the intaglio printing used on the face of the note. Completely normal.

Here a beater image, well I hope.Looks to me it messed up the printing of the E.