You can find out by taking back cover off[unplugged from mains] you will see some-where on the inside of the backcase,near the rear,or on the rear.A box with little squares,inside theese squares,you will find time of manufacture,shift number,day,and always the year.Its not a white label you look for,but the letters are stamped into the plastic.Example,6,17,99, last numbers will be your year,eg,1999.
Mr. James Devlin., March 2008