There is a national association that meets twice a year. One of those members might be willing to purchase the item based on what they collect. There must be a whole lot of those plates out there or they might be rare as hen's teeth depending if somebody went to the junk yard to retrieve each plate before the "stage" was scrapped for metal.
Or, you could go to one of their two conventions held each year with a week-long bus trip. If you hurry, they are signing up now for the next one. Happy travels....