Guinea new signature variety 500-franc note confirmed

I’m researching an interesting 1998 note variety for Guinea. As you can see, both 500-franc notes (Pick 36) shown below are dated 1998. However, the note with the AO prefix has a signature variety that’s different from the signature combination on the note with the FB prefix. The odd thing about this discovery is that the second combo is found on all other denominations in the 1998 series, as well as the 1985 series before it, and the 2006-present series.

Courtesy of Rui Manuel Palhares.