1. An article of manufacture that includes surface features that encode information according to a code, wherein: (a) each surface feature consists of a bump on, or recess in, a surface of the article of manufacture; (b) each surface feature by itself, regardless of any state of any other surface feature, encodes a sequence of multiple bits, which sequence is determined, at least in part, by a discrete elevation of the surface feature; (c) at least three different discrete elevations of surface features are significant in the code, each of the three discrete elevations occurring in one or more of the surface features on the surface; (d) surface features located in a first region of the surface encode a first copy of a complete set of instructions for manufacturing the article of manufacture; and (e) surface features located in a second region of the surface encode a second copy of the complete set of instructions.