The texture of the printing seems similar to the intaglio printing. So if there is no taped material and this is part of the note than it is very interesting and not something that could be easily done after the fact. While it is possible that this could have been something that happened after the note left the production facility there are some signs in your image that suggest that it may have been there during production.
Is the position number on the note by any chance either a 09, 19, 29, 39 or 49?
Thx for sharing