How to read Apple's serial numbers

Apple traditionally uses an 11-digit serial number for its products of the form

FF Y WW NNN MMM

where the individual parts have the following meaning

FF	factory location
Y	last digit of the production year
WW	production week number
NNN	running number, encoded alphanumerically
MMM	three-digit model number

Meanwhile, the number space is insufficient for some types of devices, and Apple also uses new 12-digit numbers of the form

FFF Y W NNN MMMM

with a similar meaning of the components as before. However, the encoding has changed:

FFF	factory location
Y	last digit of the production half-year within a decade, encoded alphabetically, omitting A, B, E, I, O, and U
W	production week in the half-year, encoded alphanumerically, omitting A, B, E, I, O, S, U, and Z
NNN	running number, encoded alphanumerically
MMMM	four-digit model number

Here is a list of the Y values:

Here are the W values: