AN-4-96 to FN-4-96 series

This series has AN-4-96 to FN-4-96 printed in the lower right hand corner, followed by either a blank,
or a series of letters always starting at "G" then descending in sequence to "A".
Once "A" is reached, a series of numbers always starting at 0 (zero) then descending in sequence to 1 follows.
Earliest known date: 29 AUG 96.