We used to brand all our pork with an electric branding iron with interchangeable letters and numbers. We kept a chart, similar to your curing book, listing each customer's products brought in, assigning code numbers, then branding each piece into the skin. In the 70's however, skinning hogs vs. scalding them became much more fashionable and we had to resort to skewering each piece with butcher twine (30 ply) and attaching metal-rimmed cardboard tags that would not disintegrate in the brine, then used indelible ink to write the code on each. When magic marker Sharpies came into being, we just knew someone invented them just for us, lol!