AN-01-06 to FN-01-06 series

This series has AN-01-06 to FN-01-06 printed in the lower right hand corner, followed by either a blank,
or a series of letters always starting at "I" then descending in sequence to "A".
Once "A" is reached, a series of numbers always starting at 9 then descending in sequence to 1 follows.
Earliest known date: 05 AUG 06.