There have been several SX70 serial number calculators offered online in the past to help decipher the numbers you find on your SX70/SLR680 cameras. Unfortunately I don't think any of them work anymore (broken links?) but luckily the info needed to manually calculate the information is readily available in the original Polaroid SX70 repair manual that I reconstructed below. I was very surprised to find that it's very easy to unscramble the numbers using the chart. All you need are your numbers and if you suck at math like me, a calculator.
This chart only covers Model 1,2,3, Alpha 1, A1M2, Sears Special, and SE cameras. I have a few numbers on what to look for to identify later Sonar and SLR680 models but chances are, if you're holding the camera in your hand, you already know what model you have. The big payoff here is finding out when your camera was born...
First, look for your manufacture code. While facing your camera, you'll find it's located underneath the upper camera back lip, just above the film door latch. It's commonly stamped with silver lettering but often times the silver is worn off and you'll need a torch light to read the stamping. If you don't see a serial number in this location, open the film door and look for a heat stamped number melted into the chassis edge. If you find a serial number in this location, you've got a grandaddy camera. :) You might see an ink stamp on the shutter frame too... that's the shutter frame ID number, not the serial number.
Ok, I'm going to use a customer's Model 1 as an example. There is commonly 11 characters designated for the manufacturing code. On most typical Model 1s, the serial number starts with a letter and only has 10 characters. If this is the case on yours, simply add a "0" in front of the letter. So the manufacturing code on this customer's camera is 0F416094273.
The numbers to pay attention to here are the first four and last two. The five numbers in between are the actual serial number. So this camera's serial number is 60942.
So using the chart, you can solve the first four numbers. The first number is the configuration or I think simply the type of shutter the camera uses. I admit I have no idea why some of these shutters are called what they are in the chart but I'd be able to identify the part differences by doing a visual inspection. Remember that often times other parts were used and replaced during repairs.
The first number (not stamped so it's designated as "0") tells us this camera has a "hybrid" shutter (still researching what that actually defines).
"F" tells us the month. A=January, B=February, C=March etc. It's important to note that the letter "I" is excluded most likely to avoid confusion when the numbers are read. So in this case, the camera was manufactured in June.
The number after the letter is the year. So this was manufactured in 1974,
Then after the year is the model number. As I mentioned before, if you're physically holding the camera in your hands, chances are you already know what model it is. This is indeed a Model 1.
Ok, here's where the math comes in and as I mentioned, there's probably an easier way to find the numbers. The last two digits designate the shift code and aren't the actual date of manufacture. You need to use a mathematical formula (crap) to decipher the day the camera was manufactured and what shift it was when the camera rolled off the assembly line.
Here's a quick formula I use is to solve for y (the actual date). z can only be either 0 (C shift), 1 (B Shift), or 2 (A Shift).