The new 12-digit serial number format makes a few minor tweaks to the format, which we have been able to decipher. The increase in length for the new format, which takes on the sequence PPPYWSSSCCCC, can be attributed to changes to the length of the P, W, and C portions of the code.
The addition of a third P digit to assist in identifying the manufacturing location is a fairly straightforward change, although it remains to be seen whether existing plant codes will simply have a character such as a 0″ appended to them or if the system is being entirely reworked. The difference in the W component is more significant, however, including a shift to alphanumeric codes that will make it a bit more difficult to decipher a machines manufacturing at a simple glance. The W change is also related to a difference in how the Y component is used.
Under the previous format, the Y component of the serial number was simply the last digit of the year of manufacture, meaning that a machine produced this year would carry a 0″ in that position. The number in that position would obviously recycle every ten years, but it should be relatively clear from Apples product release history whether a given machine was produced in 2000 or 2010.
While leaving the length the same at one character, Apple has modified the Y component to include a letter code instead of a number, and the new system will reflect in that code not only the year of manufacture, but also whether it was manufactured in the first or second half of the year. Apple has elected to use 20 different letters in this position, omitting vowels A, E, I, O, and U, as well as B. As with the previous system, letters in this position will recycle every ten years. For 2010, machines with a C in this position will have been manufactured in weeks 1-26, while machines with a D will have been manufactured in weeks 27-52 or 53. Next year will see the use of codes F and G, and so on.
