In an earlier post I pointed out that logo design "typically relies on the need to pack meaning into a small area with just a few lines and colors, often invoking symbolism to add depth to the imagery." And I encouraged readers to check out centuries-old illustrated books, many of which are now in the public domain, as a source of such content-laden imagery. Because in an earlier time we shared an understanding of a graphical language that could express concepts symbolically. While that shared understanding has been lost to a great extent, much of this old imagery retains its power and, when effectively employed, can still be evocative.
One such source of graphical symbolism is heraldry. The practice of using coats of arms to depict noble families became popular in the Middle Ages and is still employed today for civic heraldry — for cities, states and countries — as well as for businesses and associations of all kinds. While there are many books available on the topic, it's the more arcane, out of print sources that provide the level of detail necessary to be of real value to designers today. A number of these books can be browsed in the archive.org online collection, with a good example being the relatively recent A Dictionary of Heraldry, dating from 1898, some examples of which are shown below.