CAN ANYONE HELP WITH THIS JOHN DEERE DISC HARROW, BEEN IN FAMILY SINCE THE 60'S, MY GRANDFATHER PASSED IT DOWN, NEED SOME INFO ON OWNERS MANUAL OR ADJUSTING PLOW, PLEASE SEE PICS BELOW, MY GRANDFATHER SEEMS TO THINK HE PURCHASED IN 1965, HE HAS PASSED AWAY AND NOE I NEED TO LEARN HOW TI ADJUST...