A: The mark you describe was used by Villeroy & Boch. The company was founded in Mettlach, Saar, Germany, by Jean-Francois Boch and Nicolas Villeroy in 1813. The name is often associated with beer steins. The company is still in business. "Rouen" is the pattern name and "1570" is the pattern number. Now comes a bit of a detective story: The Saar Basin is an area in Germany that was occupied by France and Britain from 1920 to 1935, after the end of World War I. There are those who think the mark on your plate was used c.1885-1900, but the rimless shape and design of your plate suggest it was made much later. The Rouen line included shapes that were not used until the 1930s, so we think your plate was probably made in the late 1930s. If the plate is in excellent condition, its retail price would be $100.