Just bumping this to show what Bobby and I are referring to.
I think the ad writers of the day picked up the term and used it loosely.
By the way, Bobby has had a stock of 7 year old Mellow Mash Yellowstone which was very good, Tim gave me a taste at Bettye Jo's party from a glass supplied by Bobby and (again courtesy Mr. Cox) I've had it before. It clearly was a different version from the regular Yellowstone, older and sweeter I'd say. Both Yellowstones were very good and it is good to see our friends on the West Coast have some, hopefully they'll trade in April for some of the new Canadians I've mentioned. I may pick up some later today, so taste notes are coming.