Hopefully you were fortunate enough to get the receipt with it. When you go to get it serviced they will run the serial number. This will come back with the date it left the factory. Obviously this date could be 4-6 months prior to the actual purchase date. Being an Ultrex I seriously doubt if the "left the factory" date and actually "sold" date is much different, but it might give you a month or two extra on your warranty.