Hidden BPN and Clear BPN notes are listed in the Charlton GPMC for $100 Bird series.
It seems all the notes from AJN to AJY are hidden BPN.
Notes with prefix AJZ and AJX have both hidden and clear BPN varities.
All other prefixes have clear BPN.
So here are images from two notes one with BPN 74 and the other with BPN 66.
The note with BPN 74 is similar to the note with hidden BPN shown in the GPMC. So its Cat. No. would be BC-60a or BC-60aA.
In your opinion is the image with BPN 66 from a note with clear BPN or is it also from note with hidden BPN? In other words would the note with BPN 66 be BC-60a, BC-60A or BC-60a-i, BC-60A-i

