Very scarce wall plaque measuring

Very scarce wall plaque measuring 5 ¾ " X 8 ¾ ". The front reads:- William Wilberforce 1759 – 1833 M P For Kingston Upon Hull and Yorkshire, Emancipator. Abolition of Slavery Act 1833. The back of the plaque has the Eastgate Pottery Withernsea stamp. Made in England. We contacted Eastgate Potteries in Withernsea, UK for more information. The Director, John D. Worsdale responded with this note, "This was one of a limited number of plaques manufactured in the 1970's, as a special commission for William Wilberforce House. There were only 50 plaques made. I have never seen one for sale, therefore I cannot give you an estimate on value...It is extremely rare."