There are ink smear errors that can happen on either side of a note and in either black or green ink.
https://www.pmgnotes.com/news/artic...smear-error/ Sometimes they look more like a big ink stain when you look over typical examples or in books. This is blob like which looks a bit more like something dropped onto the note after the fact at first, however sometimes there are blobs of ink also similar to the one posted and like this example (one of many from heritage auctions currency sold listings) that have been graded and sold so it appears to be a genuine ink smear error.

Edited by datadragon
05/09/2023 6:46 pm