Winchester wall serial numbers and dates sometimes don't match very closely and the dating differences & uncertainties you describe are not uncommon. The dates of receipt into and shipment out of the factory shipping room are available from the Cody Museum for most rifles in your date range, but the shipping destination is not normally shown in the records. Special-order feature details are often given but please be advised that many, many wall tangs have been replaced and substituted over the years. A Museum 'member' can get the serial # info over the phone for free but I'm not a member so you're on your own here.
Good luck, Joe
