What is the difference between a Wide and Narrow Panel note?

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Can someone please tell me what the difference is between a wide and narrow panel note?
Does it only exist in the 1937 series and if so what denominations?
Is there a simple way to determine the difference between the two types?

To the best of my knowledge narrow and wide panel exists in the 1937 $1 note with the signatures Gordon Towers.
Narrow panels will have the prefix either HA or JA and
Wide Panels KA-ZA, AL-ZL, AM-NM, and OM (according to the cat)

The narrow panel notes are worth more than the wide panel notes.
 
According to the cat the narrow and wide panels can be easily identified by the spacing of the King's portrait medallion from the notes border. The narrow signature variety has a wider space between the top of the kings portrait  and the top border. The wide signature panel variety has a very narrow space in the same area. I hope this helps

FRIEDSQUID