We used to include a QR code on product labels with the serial number. This is so that sales staff can scan in serial numbers to delivery notes and track stock. This is not uncommon.
This example barcode has a simple serial number 2900-0000-0000 which is great if you want to know the serial number, as we do.
However, QR codes are starting to be quite common and most phones will just read them, even in the camera app. This is somewhat boring being just a serial number. People are actually used to QR codes having useful URLs to take them to a web site.
So, we came up with a cunning plan. This was actually to help one of my friends with some work he is doing for a customer, and we came up with this plan between us, and it works quite well.
The trick is making the barcode useful to us as a serial number but also useful to random people reading it on their phone.
HTTPS://FB0.UK/290000000000 in it, as an example.
As you see, you can fit a short domain like that, and 12 digits of serial number, in the same minimum size QR code. We had to lose the hyphens, and stick to upper case, to fit without being a more dense QR code or taking more space.
When scanned, you get to the FireBrick web site, and indeed to the FB2900 product page which includes a link to the quick start guide, etc. This makes it actually a useful barcode for anyone pointing their phone at it.
For our systems, we can easily make them strip the initial HTTPS://FB0.UK/ (and add in hyphens to look nicer). So we can use it as a serial number just as we did before.
Bingo, dual use QR codes.