This image snagged off the Fox forum, not my gun. That said, mine also has the corrugated metal strip. Discussion has it that they were used for some Philadelphia guns. In the blackened stock head area on mine I can see one stamped number in the wood and it is one of the numbers in my SN so.... more info to suggest the stock is original. Maybe when the blackened oil is removed, I will be able to see more numbers.
Cheers,
Jack