Not sure if it would be considered dinner or luncheon plate. It measures slightly over 8 3/4 inches. I believe the pattern is Dubuque by Buffalo China. Please see photo # 2 for the complete backstamp. I've always thought there were stamped numbers or letters below the backstamp that has been worn away. I can't get the faint impression to show in the photo. Since I am not an expert, I am not comfortable rating the condition, it is easier for me to describe and provide detailed photos...