This only applies to Canon L (Luxury) lenses. Consumer type of Canon lenses (non-L) does not have these codes. Take note that this code is NOT the serial number of the lens, it is the production code printed at the rear mount of Canon L lenses.
First alphabet “F” shows the production plant:
U = Utsunomiya, Japan
F = Fukushima, Japan
O = Oita, Japan
Second Alphabet “K” tells the year of manufacturing. In this case, the K is referring to production year of either 1996 or 1970 or 2022.
The next two digit codes tell month of manufacturing. 05 means manufactured in May.
The last two digits should represent the production count. Unsure at the moment.
So, in summary, FK0582 means that the lens was manufactured in Fukushima plant in May 1996 (most likely).