Duke of Norfolk Coat-of-Arms - High Street, Arundel, UK - Coats of Arms on Waymarking.com

The plaque, cut in stone, shows the coat-of-arms of the Duke of Norfolk.

Wikipedia has an article about the 16th Duke of Norfolk that advises:

Bernard Marmaduke Fitzalan-Howard, 16th Duke of Norfolk, KG, GCVO, GBE, TD, PC (30 May 1908 – 31 January 1975), styled Earl of Arundel and Surrey until 1917, was the eldest surviving son of Henry Fitzalan-Howard, 15th Duke of Norfolk, who died when Bernard was only 9 years old. His mother was Gwendolen Fitzalan-Howard, suo jure Gwendoline Mary Herries, 12th Lady Herries of Terregles, and he inherited her peerage when she died in 1947.

He was educated at The Oratory School and was commissioned into the Royal Horse Guards in 1931, but resigned his commission in 1933. He joined the 4th (Territorial Army) Battalion, Royal Sussex Regiment in 1934, and was promoted Major in 1939. He served in World War II, in which he was wounded in action.

As hereditary Earl Marshal, he organized the coronation of King George VI and Queen Elizabeth, the coronation of Queen Elizabeth II, the funeral of Winston Churchill, and the investiture of Prince Charles as Prince of Wales. He was a keen cricket fan and was the manager of the English cricket team in Australia in 1962–63, which excited much press interest.

Wikipedia has an article about the Duke of Norfolk that has a section about the coat-of-arms that advises:

The heraldic achievement of the Howard Dukes of Norfolk consists of four different elements: the arms (or shield), the crests, the supporters, the motto, and the batons of the Earl Marshal.

• The Arms: Quarterly 1st Gules on a Bend between six Cross-crosslets fitchy Argent an Escutcheon Or charged with a Demi-lion rampant pierced through the mouth by an arrow within a Double Tressure flory counterflory of the first (Howard); 2nd Gules three Lions passant gardant in pale Or, Armed and Langued Azure, in chief a Label of three points Argent (Thomas of Brotherton); 3rd Checky Or and Azure (Warenne); 4th Gules a Lion rampant Or, Armed and Langued Azure (Fitzalan).
• The Crests: 1st On a Chapeau Gules turned up Ermine a Lion statant gardant with tail extended Or gorged with a Ducal Coronet Argent (Thomas of Brotherton); 2nd Issuant from a Ducal Coronet Or a pair of Wings Gules each charged with a Bend between six Cross-crosslets fitchy Argent (Howard); 3rd On a Mount Vert a Horse passant Argent holding in the mouth a Slip of Oak fructed proper (Fitzalan).
• The Supporters: Dexter a Lion, sinister a Horse both Argent the latter holding in his mouth a Slip of Oak Vert fructed proper.
• The Motto: Sola Virtus Invicta (Virtue alone is unconquered).
• The Batons: Placed behind the shield are two gold Batons in Saltire enamelled at the end Sable (black), which represent the Duke of Norfolk's office as Earl Marshal and Hereditary Marshal of England.

Often, the coat of arms of the Duke of Norfolk appears with the Garter circlet of the Order of the Garter surrounding the shield, as seen in the arms of Miles Stapleton-Fitzalan-Howard, 17th Duke of Norfolk. However, this is not hereditary; the 17th Duke did not become a Knight of the Garter until 22 April 1983. The 18th Duke of Norfolk, Edward William Fitzalan-Howard, as of 2016 had not been awarded the Order of the Garter. No order of knighthood is necessarily a component of the coat of arms of the Duke of Norfolk.

The shield on the bend in the first quarter of the arms (shown to the right) was granted as an Augmentation of Honour by Henry VIII to Thomas Howard, 2nd Duke of Norfolk, to commemorate his victory at the Battle of Flodden. It is a modification of the Royal coat of arms of Scotland. Instead of its normal rampant position, the lion is shown cut in half with an arrow through its mouth, commemorating the death of King James IV at the battle.