The Roman military decoration was subsequently employed in European heraldry, where the term denoted a crown modeled after the walls of a castle, which may be tinctured "or" (gold), "argent" (silver), "gules" (red), or "proper" (i.e. stone-coloured). In 19th-century Germany, mural crowns (') came to be adopted for the arms of cities, with increasingly specific details: "Residential (i.e. having a "royal" residence) cities and capital towns usually bear a ' with five towers, large towns one with four towers, smaller towns one with three", observed Arthur Charles Fox-Davies, in "A Complete Guide to Heraldry", adding "Strict regulations in the matter do not yet exist" and warning that the usage was not British.