When the appraisers on the "Antiques Roadshow" appraise china, porcelain or anything like that, the first thing they do is turn it upside down and look for marks to see if they can find out anything about the maker or the year.
Sometimes the marks are clear and familiar and tell who made it and when. Sometimes, they just get the maker, but no year. Sometimes, the piece is completely unmarked and the appraiser has to make an educated guess about the piece's origin. Suffice it to say, the more genuine marks a piece has, the better. It's easier to appraise accurately.