Dean,
That Fox serial number chronology that Lightner Library first put out back in 1976, and is now available various places on-line for free, is worth just what you pay for it. The only way to really know for sure is a letter from Savage --
https://www.foxcollectors.com/mechan...actory-letters
Letters were pretty good when we had Roe Clark and then John Callahan as the historians doing them, but we've heard somewhat dismal reports on the letters since Savage took over doing them. Hopefully they will get better.
Better yet would be our friend Toolman talking his way into Westfield and bringing those boxes of old production cards home to the A.H. Fox Collectors Association, Inc.!