Just because the dishware has the number 1603 does not mean that it was made in 1603. Sometimes, when we see a year number on the underside of a plate, it refers to the date the pattern was introduced.
Look at the marks on the bottom of the plate and Google image any other marks that you do see. This will tell you who made the dishware. Various changes in back stamps indicate when the item was made.
You can check out information in a book: "Kovel's New Dictionary of Marks Pottery and Porcelain 1850 to Present" by Ralph and Terry Kovel; or "Kovel's Dictionary of Marks Pottery and Porcelain 1650 - 1850" by the same authors are decent basics. Also, "Miller's Antique Marks" by Judith Miller is an excellent reference book.