I do remember it was a large 2D barcode. Like QR but with a square in the middle. (AZTEC?) I was trying random barcodes I had lying around to test my own compo

I do remember it was a large 2D barcode. Like QR but with a square in the middle. (AZTEC?) I was trying random barcodes I had lying around to test my own component. The one with the zero byte happened to be a large one they had added to my passport when I visited the USA. It had "US-VISIT" printed next to it in big letters. The device was a rugged industrial handheld device with a screen and a camera, designed for mailrooms and warehouses. This was around 20 years ago and I remember the OS (including the barcode component) was completely bespoke and it ran without any process protections. This meant that the barcode would crash the whole device and you had to perform a hard reset.