Canon FD lenses are old lenses produced for Canon film cameras. FD lenses were manufactured first in 1971, and were the leading type of Canon lenses until being replaced by the EF lenses in 1987. Canon FD lenses are still available from private sellers, and can be purchased for use on older Canon FD-mount film cameras. However, as the lenses are older and subject to mechanical failure, consumers should be aware of the date of manufacture before buying a used Canon FD lens.
Look on the back of the Canon FD lens where the lens would be mounted to the camera and find a six-digit serial number. The number will be written as a single letter, four numbers and then one final letter.
Examine the first letter in the serial number, which designates the year of manufacture. The letter "L" stands for 1971, and the years continue sequentially through the alphabet (e.g. "M" is 1972, "N" is 1973 and so on). The alphabet starts back over again in 1986, when "A" designates lenses manufactured in this year.
Look at the following two numbers, which designate the month of manufacture. The two numbers will match the number of the month with, for example, "03" representing March and "11" representing November. If your serial number is only five digits long, it is possible that a "0" is omitted in this month code.
The next two numbers, if present, are internal Canon codes that do not correspond with the date of manufacture.
Older lenses are not necessarily worse than newer lenses, as a well-maintained and cared-for lens will function better than one that was not taken care of. While the date of manufacture may be useful for historical purposes, you should judge the quality of the lens based on its mechanics rather than its date.