Rob, that is interesting that Lionel Carter owned a card with the F stamp. I wonder if he owned it because he believed it belonged to Fitzgerald, or if it just happened to turn up among the cards in his collection? I dug around a little, but could not find much more about the stamp.
Here was the thread in June where the Obak came up along with the earlier thread with the theory about the daughter and the story of the sale.
www.net54baseball.com/showthread.php?t=169794
www.net54baseball.com/showthread.php?t=89645
Here is a site that lists the F back as "unclassified"
www.thegreatt206backstampproject.yolasite.com