A slipped digit in the serial number1
A nice error to find. I would expect it to have some premium over face value.
Value would depend on how common an error it is for the Euro notes, and on the grade of the note.
Your not is quite well circulated. Some collectors (myself included - I collect Irish error notes) are not fussy on grade for error notes.
The value of an error note also depends on how serious an error it is. Generally, errors with extra paper tend to do well, as do missing print errors, and errors on replacement notes.
