It’s for quality control, so if a lot of defective bottles are coming off the line, they’ll know where to start looking for the problem. Bottles from a single manufacturer will have many different dot patterns, so by the time the product gets to you, you probably have bottles from various parts of the manufacturing grid and therefore various dot patterns.

To translate the code into useable information, the bottle-maker illuminates the bumplets, then scans them with a light meter hooked to a computer. Newer technology allows printed codes to be scanned directly, so you’ll eventually see fewer dots and more readable letters and numbers.

The flip side is, there are more dots on the bottom of a bottlew. Beer bottles have concave or lumpy or otherwise marked-up bottoms to keep the wet glass from creating a vacuum when it’s placed on a flat surface, so you don’t lift the table off the floor when you pick up your drink.