These pages are from the front of the Kohler service manuals   1965 - Serial begins with a letter - A 1966 - Serial begins with a letter - B 1967 - Serial begins with a letter - C 1968 - Serial begins with a letter - D 1969 - Serial begins with a letter - E 1969 -  7-digit serial number - First two digits 10-19 1970 -  7-digit serial number - First two digits 20-29 1971 -  7-digit serial number - First two digits 30-39 1972 -  7-digit serial numb