This disclosure relates to advanced image signal processing technology including encoded signals and digital watermarking. One claim is directed to a container comprising: a 3004 or 3003 aluminum alloy shell, the 3004 or 3003 aluminum alloy shell comprising an outer surface and an inner surface; a 5182 aluminum alloy lid attached to the 3004 or 3003 aluminum alloy shell; and an opaque ink printed on the outer surface in a 2-dimensional pattern according to a machine-readable signal. The outer surface and the opaque ink printed on the outer surface comprise a spectral reflectance difference at a machine-vision wavelength in a range of 8%-30%, and the machine-readable signal is detectable from imagery representing the opaque ink printed on the outer surface. Of course, other containers, technology, methods, packages, objects, systems and apparatus are described in this disclosure.