I think the existing line should've been edited rather than a new one being added. I can't find evidence of a 2011 note with Sanusi/Umar signatures existing. It seems the switch happened in 2012, with 100 and 200 naira for that year having both Sanusi/Nda and Sanusi/Umar, and the rest of the denominations having only Sanusi/Umar.
I think the existing line should've been edited rather than a new one being added. I can't find evidence of a 2011 note with Sanusi/Umar signatures existing. It seems the switch happened in 2012, with 100 and 200 naira for that year having both Sanusi/Nda and Sanusi/Umar, and the rest of the denominations having only Sanusi/Umar.
You're right. I've made the correct adjustments now. Thank you!
Vladimir
Catalogue Administrator and Banknote Master Referee.
I believe that 2011 was a year with print issues. My own note is a significantly paler shade and I have seen notes with misaligned dates and even index number errors for 2011. Was there a 2012 note printed, or did they jump to 2013?