$100 bill, is this a stamp or an error?

Cant tell if this is just a stamp from a bank or similar or if it's some sort of ink transfer error. Any ideas from the pics? Im leaning towards just a stamp.

 

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Not an expert here but looks like a stamp.

It is a star note for sure

 

It is a tellers stamp. After the bundle is strapped, the teller stamps it with their stamp and it sometimes goes off of the band and onto the bill. Not an error. Spend it.

 

+1

 

Or, possibly stamped for authentication in a foreign country. No, not an error.