Hello, it's me again.
As I understand, the Birds $50 notes currently have prefix FM*, even though most of our $50's have denominational letter "H", and despite of our FM*'s on our latest $50's, I predict that the new Journey $50 will start with prefix AHA, since there have never been any $50 notes printed by BABN - there is speculation that the new Journey $100's will be printed by CBN with the prefix EJ*'s since all of our previous $100's (1975 and 1988 series) have been printed by BABN, so I really think that the CBN should take a stab at printing our new $100's and BABN should take over our $50's for awhile.
By the way, if we do see AH* $50's, we will probably see BHA after AHZ, and after BHZ we might see BMA since AM*'s were used on our $1 notes way back when.
See what you think.
Later, Jonathan