Ok, I think a lot of info is being confused in PM's on different bikes. A 24,000 series is 1968. Sabre's were made from 1968' to 71'. For 1970 on until the bankruptcy in late 71' they used a sticker for the Vin#'s attached to the center on the top of a Tecumseh round Air Cleaner.
So You have a 28,000 series stamped into the frame so I would say somewhere in that mix a late 68 or a 69' . I hope this clears a lot up. Sometimes info can be misunderstood in a PM than in a real phone or in person conversation. Too many bikes so little time. LOL