Post 11/2011 they changed to alpha, 4 numbers, alpha, the first letter being the month, A for January, the last being the year, B for 2011, C for 2012, etc. - The Guitar Dater Project will decode W, S, I and who knows what other prefixes [factory codes].
I do not know how accurate the system is but the few I've run have worked just fine. Plate serial numbers have nothing to do with headstock serial numbers.
F is the production factory which stands for Fujigen.
I'm not sure what year the changeover occurred but using the formula it will be easy for you to tell.
Ibanez did not put serial numbers on their guitars. The only way to date these guitars is to find out what years they were available and then comparing all the minute details like scripts, contours, and inlay variances that only the hardcore vintage gurus know.
These guitars can be dated by their electronics if they are original.
- Under the old numbering scheme 1997 would show duplicate numbers to 1987 so the serial number was changed to the F and 7 digits, now the first 2 denoting year of production. The last 5 numbers will be the consecutive number denoting production count for the year with the caveat that each month will start at predetermined intervals of 3000 or 5000, etc. With production year beginning in November - 00000 - Shown as F for Fujigen in the examples above, other factories used that mainly produced the budget models were C for Cort [Korea], S for Samick [Korea], W for World [Korea], and guitars are also built in I Indonesia, China, and who knows where else.
These serial numbers are usually quite different from the MIJ numbers, have many extra digits because of the enormous volume of guitars produced, and I am not familiar enough with any of them to tell you how to figure out the dating.