Coming back to this.
Looking through the db, there's a pretty clear cutoff for LOS. January cars generally have black ashtrays, February cars (and a couple Jan cars) have woodgrain. NOR is surprisingly similar, but with a bit more mixed at the cutoff.
Real problem is the data isn't absolute - no telling what's been done to a car after 40-50 years. So that's as definitive as it may ever get...