Canon 5D Mark III Manual, Page 107:About the Lens Serial Number
- In the step 3, if "*" appears in front of the 10-digit lens serial
number, you cannot register several copiers of the same lens model.
Even if you enter the serial number , "*" will remain displayed.http://gdlp01.c-wss.com/gds/8/030000734 ... m-c-en.pdf
Basically if you have two lenses that are identical, you will not be able to calibrate both differently (In the circumstances where the "*" is visible), the first one will use the same settings as the other. As far as I understand it.