1939-? Ceramic Blue & White Plates

Hello, I’ve got three plates. Not sure if any of them are worth anything, but that is what I hope to find out. There appears to be the same symbols on the back of all three, I do not know what they mean. There is a date on the front of one that reads 1939, and another plate has a year on the back that is either 1991 or 1661. Im guessing it is 1991, but Ive got no clue. It would really help if anyone could shed some light on these plates and explain them to me. They are in great condition and the blue on white is truly beautiful.