European Monetary Union 50-euro note oddity reported

Does anyone have any information about this 50-euro (Pick 4) note which appears to have CC3 printed near the 50 denomination in the lower right rear? The person reporting this note says it appears the CC3 was printed at the same time as the rest of the note, not as an overprint, but it’s hard to confirm based upon the scans provided. In any event, if you’ve seen other such notes or have any ideas on how/why it was created and what it’s worth, please post a comment.

UPDATE: Thomas Krause recommends this web site which shows hundreds of different stamps applied to euro notes.