+1

I have a lot of experience with Schwinns that have both color and parts anomalies with respect to catalog specification, so as far as I am concerned, the catalog spec's should always be taken as +/- 1 year, depending on what time of year the frame was numbered.
Schwinn never intended that the customer would later be referring to the serial number to match their bike to a catalog, and changes in production methods and parts inventories were happening year-round.
They just weren't all that concerned with model year specification back then. Inventories and orders of parts and colors were apparently given far more consideration than having the serial number date agree with that year's catalog spec's, and likely the inventory people (parts), manufacturing people (paint) and marketing people (catalogs and orders) were operating independently to a degree.
It sometimes seems that almost half of the Schwinns out there have mixed-year spec's.