John Lehman found my blog and asked me to share his expertise on Coats of Arms and Heraldry with you. Since I knew little about the subject, my curiosity was piqued. John’s Coat of Arms database website has encyclopedic information on this 
topic. While he “only” has 9,500 arms thus far, he intends to add hundreds of thousands over the years from all areas of Europe and he hopes to serve as the world’s largest heraldry database. My questions to him were why would a genealogist want to search for a “COA” and what info does it give us about one’s ancestors?
His answer:
“I would say that it gives them some clues about their family history. The symbols on the arms have meanings, many of which have been lost to history, but some of which we can still make an educated guess. For example, a Moor’s head in the arms may indicate that their ancestors were victorious in the Crusades. Another example would be a fret or lattice, which may mean the family was involved in the fishing industry (the symbol may signify a net). Sweeping meanings are controversial though, and some think them to be an invention of the Romantic era, so they must be taken with a grain of salt.
I would also say that some arms do come with biographical notes that the genealogist/herald wrote down. Such information may be helpful to those doing research. For example here is one of the notes Burke recorded for the surname Irvine: ‘(Lowtherstown, co. Fermanagh, bart., extinct 1690; confirmed by Erskine, Lord Lyon, 1673, to Lieut.-Col. Gerrard Irvine, of Castlefartagh, second son of Christopher Irvine, Esq., of Castle Irvine, who was created a bart. 1677). Motto—Dum memor ipse mei. (Killadeas, co. Fermanagh; descended from John Irvine, d. 1716, brother of Christopher Irvine, Esq., of Castle Irvine).'”
On his site, he offers a wealth of information. Happy hunting.
ALL IN YOUR FAMILY 