Idaho Falls, Idaho. $20 1902 Plain Back. Fr. 650. American NB. Charter #6982. Very Fine.While many small size examples are seen, large size are genuinely scarce with only nine reported to the current census, according to the National Bank Note Census. This is the only $20 known on the bank and is seen with good signatures and overall eye appeal. A light stain is noted at top center and at cashiers signature panel.