Home Forums Hardware Mac Desktops & Notebooks new serial number format musings

So I got that itch again this morning, and actually managed to dig up enough information that I could tease out the full rules for Apple's new serial number format

# 11 digit:
# 0-1 = plant code
# 2 = year of manufacture
# 3-4 = week of manufacture
# 5-7 = unique unit code
# 8-10 = model code

# year is last digit. repeats every 10 years, "4" could be 1994 or 2004 etc
# week is two digits, 00 through 51, week of year

# 12 digit:
# 0-2 = plant code
# 3 = year of manufacture
# 4 = week of manufacture
# 5-7 = unique unit code
# 8-11 = model code

# apple is using a "base-27" numbering system for year and week, the digits are: 123456789CDFGHJKLMNPQRTVWX
# the number notably does not include vowels AEIOU, and consonants BSYZ
# the year starts in early 2005 with 0, 1 is late 2005, 2 is early 2006, M is early 2014, etc
# the week code is the number of weeks offset from the year. (either starting with the first or 28th week)
# 0123456789CDFGHJKLMNPQRTVWX are weeks 1-27 and weeks 28-54
# (all years have 52 weeks plus one or two days, so the system must be able to handle 54 weeks)
# how apple interprets years when it hits 2018 is unclear. X is early 2018 but is 0 or Y late 2018?
# or will X be skipped and 0 be used for early 2018?

(before the change, 11 digit numbers were computer serials, 12 digit were service part serials, now 12 is computer, and iirc 17 or 18 are part)

As my notes indicate, I don't know what will happen in 2018. Apple needed to have at least a base-27 (not base-26) number system for this to work, because there are more than just 52 weeks per year. Since they exclude vowels and BSZ for robustness, they could go through to y (unless counting it as a vowel I suppose) though only needing to apply it to the year component, but no one seems to know for sure. If we stick with 27 and not 28, then when it wraps, 0 won't represent early year, it will represent late year, which also doesn't look too clean, possibly suggesting X will also be skipped when it wraps.

So what do you think they have in mind?

(this is kinda unfortunate, as it makes it a lot more complicated to figure out the manufacture date by eyeballing the serial number, I will miss that)

on a related note, does anyone happen to have a chart (even an incomplete one!) of the model codes? This is what I happen to have:

Not that it matters much, but these are not numbers I recognize as complete and independent ID sequences (like Order Number, Model Number. EMC Number or Model Identifier), except that they may be part of serial number series. Whatever their provenance, you can successfully search for them in EveryMac.com's Ultimate Mac Lookup. Unfortunately, I'm not aware of the reverse option, i.e, a way to use that lookup to generate a list of such code snippets.

on the off chance that I'm not the only one on the planet that needs this information, the correct character lookup table appears to be

"0123456789CDFGHJKLMNPQRSTUVWXYZ"

I had to add "S" since I just noticed we have a bunch of iMacs with that code that were looking up wrong since it wasn't in my lookup earlier. ("S" is "late 2016") I assumed they were skipping all the letters that looked like numbers (b/i/o) or other letters (e). I don't know what they thought "a" might be confused with.

If this format holds past "early 2020" and they want to drag it out, they'll probably give up and use a, b, e, i, and 0 at the end also but I have no way to predict that.

I can't believe I googled all over for this information and found nothing more useful than my prior post...

MacRumors posted an article back in 2010 with a partial explanation of the 12-digit serial number format, at least the general structure and how to decode the date. Apple legal asked MacRumors to remove the article and they complied, but there were reposted copies around.

Based on that article, your list of characters is almost right, but there are slightly different lists for the half-year and week.

The half-year list starts with C for the first half of 2010, and goes up to Z for the second half of 2019, skipping vowels, thus "CDFGHJKLMNPQRSTVWXYZ".

The week list starts with 1 for week 1 in the half-year and goes up to Y for week 27, skipping vowels, B and S, thus "123456789CDFGHJKLMNPQRTVWXY".

It appears vowels were skipped as an arbitrary choice, but B and S were skipped in the week list because of potential for visual confusion with 8 and 5 in that position. It was not necessary to skip S in the half-year list because 5 is not used there.

For 2020 and later, Apple will probably change the serial number format again, most likely extending it at least one more character. Then we start all over again trying to decode them.

the week codes only require
0123456789CDFGHJKLMNPQRSTUV
normally it'd be only 26 characters (not 27) since they need to cover the weeks in the first or last half of the year, but leap years have one more week (with one day in it) so they extended the list to 27 characters. the last day in the leap year is coded as latter half of the year, week 27.

I'm pretty sure they removed I and O to avoid confusion also with 1 and 0, not just because they are vowels. Considering how hard it's getting to read them and how they all have barcodes on them now, apple may just do away with that and "reuse" those previously shunned characters if they run out of address space before they change formats again.