Early Mac Serial Number Decoder

Welcome to the pickle's Macintosh serial number decoder. The decoder script has undergone a thorough revision and now supports more models than ever before. If you run across an unsupported model, e-mail me with as much data as you know about the computer (model, model number, CPU speed, where it was made, when it was made, etc.) and I may be able to add support in a future revision. A big thank-you goes out to everyone who submitted serial numbers in the last year or so — you've helped to improve the decoder immensely!

I'm looking for Apple II-era serial numbers and accessories, along with Apple III and Lisa data. If you can help, please e-mail me with all the data you have. I could also use a hand with other Mac accessories, particularly from the beige era. If you have keyboards, monitors, mice, or other accessories with a serial number, e-mail me as much data as you can about them and I'll see what I can do.

How To Use This Decoder

To use this decoder, simply type in your Mac's serial number (the decoder is case-insensitive) and click the Decode button or press return/enter. Any spaces or asterisks can be left out, as they are not considered to be part of the serial number. I have expanded the regex string matching, and just about any serial number from any Mac hardware will validate. If you get the "invalid serial number" message and believe the serial number to be valid, please e-mail it to me, along with a thorough description of the product.

Important note: if what you think is the serial number starts with "BCG", congratulations! You've found the FCC ID. The two are commonly confused on early Macs, particularly the 128. Early Macs had the serial number located below the lower-left corner of the screen, not on the back. Some Mac Plus models had the serial number sticker on the bottom of the case. If you enter an FCC ID by accident, the decoder will remind you of this and instruct you where to look for the proper serial number.

The Decoder

Your Mac's serial number:

If You Get an Error

If you get an error or "unknown" value, e-mail me the serial number string you put in, along with as much data as you know about the Mac. This includes the specific kind of Macintosh it is, approximately when it was made, etc. I can't do much of anything if you don't tell me what Mac you're trying to find out about!

Don't worry. If you e-mail me, I won't share your name or any other personally identifiable information with anyone, although I reserve the right to use the serial number in collaboration with other developers for the purpose of improving this decoder.

Supported Apple hardware

(* indicates some models may not be recognised):

Known Bugs

How It Works

WARNING: Geek alert! If you don't like math, you can skip this section.

The methodology behind this decoder is reasonably simple. The prefix consists of one or two letters (and/or numbers) designating a factory code:

In our example serial number, F 4412SAM0001, we see that the Mac in question was made in Fremont, California.

The first numerical character* indicates the last digit of the year of production. In all cases prior to the Mac Plus, this will be in the 1980s. Referring back to our example again, we see that the Mac with serial number F 4 412SAM0001 was made in 1984.

* Not always. In 1990 and 1991, a number of Macs were made at Fremont with "F1" or "F3" as the factory designator, and modern build-to-order Macs may have a number preceding the letter in the factory code.

The next two digits indicate the week of the year of production. In our example, we see that the Mac with serial number F4 41 2SAM0001 was made in the 41st week of the year.

The next three characters are a three-digit base-34 unique identifier. (The letters 'O' and 'I' were not used, presumably to avoid confusion with the numbers zero and one.) If we assume Apple began each week at 000, this identifier becomes an ordinal indicating the model's production order that week. Our example is number F441 2SA M0001. To convert this from base-34 to decimal:

2 =  2, so:  2 * 34^2  (the "hundreds" place) = 2312
S = 26, so: 26 * 34^1  (the "tens" place)     =  884
A = 10, so: 10 * 34^0  (the "ones" place)     =   10

So, our example was the 3206th Mac produced that week. It is interesting to note that this system allows for a per-model production capacity of 39,304 Macs per week, or just over two million per 52-week year, assuming duplicate unique IDs from different factories are not allowed.

The remainder of the serial number is the model number. In our example, we see that the Mac with serial number F4412SA M0001 has a model number of M0001, indicating it is a Mac 128. Later models use a three-character code in place of the model number; perhaps Apple was running out of serial number ink?

Last Modified on 02 December 2005.

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