Unless I am misremembering, I vaguely recall reading something about an alternative method of identifying an F-169. Regretfully I do not have any way of determining my original source of that information.
I believe that it might have had something to do with the position of one of the N's in PENNY. Unfortunately, in many instances, if the date was too worn to determine the position of the 1, the same situation existed for the lettering in PENNY.
As I stated in the beginning, I might be merely misremembering, simply incorrect, or just delusional...