On this date 624 years ago, King Richard II gave the verdict in the most famous case, and one of the earliest, in heraldic law. One Richard Scrope, 1st Baron Scrope of Bolton, Yorkshire, and Sir Robert Grosvenor of Cheshire, while participating in King Richard II's 1385 invasion of Scotland discovered that they bore identical coats of arms. Scrope sued Grosvenor.
After a trial in military court involving hundreds of witnesses including Geoffrey Chaucer, the "Father of English Literature" and author of The Canterbury Tales, Grosvenor lost the case and picked a new coat of arms. (A summary of Chaucer's 1386 deposition is here.) That coat of arms is still used in by the family's descendant, Gerald Grosvenor, 6th Duke of Westminster, the #1 richest person in the UK on the Forbes list and #89 globally as of March 2013. His eldest son, Hugh Grosvenor (Earl Grosvenor) is godfather to Prince George, third in line to the monarchy of England and the Commonwealth realms. (Grosvenor is in the photo below as the second from the left person in the foreground row of individuals--the young clean-shaven chap wearing a suit and tie; click to enlarge, more details below.)
Heraldry is more than 900 years old and still used, perhaps most notably in England, Scotland, France, and Canada, but in most nations of Europe as well. It was originally a way to visually identify yourself on the battlefield. By the 1200's they became a sort of familial logo.
Formal rules of heraldry persist; officers of arms oversee heraldic matters in some countries.* Only an individual, not an entire family, can possess a coat of arms, there can be no identical coats of arms between any two individuals, and a coat of arms can be inherited as legal property from father to eldest male heir.** A system known as cadency adds small variations known as brisures to a living inheritor's coat of arms to distinguish it from the elder's coat.***
Azure, a Bend Or
The formulaic description of an heraldic achievement, the overall heraldic display for an individual and of which a coat of arms is the main part, is called a blazon, from the French blason, "shield", and uses in part technical Norman French terms. A coat of arm's blazon's grammar at its most elementary level first describes the field (background), field-related elements including tinctures (colors and metals),**** then charges (emblems, devices), and if necessary in a clockwise manner beginning from the dexter (left) and chief (upper) position.
Scrope's arms (shown above) being very simple are blazoned merely "Azure, a Bend Or", meaning blue (azure) with band/strap (bend) golden (or). A bend runs upper dexter to the lower sinister unless described otherwise.
A complex example from an old original coat of arms (c. 1619), Winston Churchill's arms (shown here) are blazoned as follows, the significance of all the elements of which indicate Churchill's genealogy (both Churchill and Spencer arms) and honors history. See and read about Churchill's entire heraldic achievement (his "armorial bearings") here. Note that a coat of arms and especially the heraldic achievement can change during someone's life according to heraldic rules.
Quarterly 1st and 4th Sable a lion rampant on a canton Argent a cross Gules; 2nd and 3rd quarterly Argent and Gules in the 2nd and 3rd quarters a fret Or overall on a bend Sable three escallops of the first and as an augmentation in chief an inescutcheon, Argent a cross Gules and thereon an inescutcheon Azure, three fleurs-de-lis Or.
Photo; click to enlarge: Earl Grosvenor at Prince George's 2013 christening, here seen between James and Pippa Middleton, brother and sister of Catherine ("Kate") Middleton, Duchess of Cambridge, wife of Prince William, Duke of Cambridge, second in line to the English and Commonwealth thrones.
**In Canadian heraldry a woman can inherit and transmit arms as a result of the Canadian Charter of Rights and Freedoms (1982).
***There are no such things as "family crests". Selling them is a scam. A crest is a small part of an heraldic achievement, the main component of which is the individual's coat of arms. To use a coat of arms without being descended from the original grantee is usurpation.
****There are five traditional tincture colors and two traditional tincture metals but non-traditional ones exists; in Canadian heraldry, Rose is officially recognized as a color and Copper as a metal.