Ron, we don't know of any way to date the mower from its serial number. Our SB guru, Deejay, believes that the numbers were not orderly and no records of numbers have survived. If your mower has a Briggs engine and it is the original one, give us the Model, Type and Code numbers (stamped on the cooling air cowl) and we can tell you when the engine was manufactured. The mower will have been made several months later.