Your plates were made at Stoke-on-Trent in England. It begin with Josiah Spode. In 1847 william Copeland became the sole owner. Now I cannot read your mark, it’s very blurry. According to Kovel’s the word Copeland on top of emblem. In the middle of emblem the word Spode. The bottom of emblem England,then mark changed again to W,T. Cpoeland & Sons years later. In 1976 it became Royal Worchester Spode. It is still in business today. So as to how old I do not know nor the value, Prices are all over the map on e-Bay Kovels have some plates listed from 19th century for $20-30.00 each.