These variations are effectively exploited in the Scottish system of cadency.
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Marks of cadency are almost unknown, and shields are generally very simple, with only one charge.
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In English heraldry, they are used in many different ways, and can be the cadency mark of the sixth son.
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Canadian cadency generally follows the English system.
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They are subject to a system of cadency to distinguish between sons of the original holder of the coat of arms.
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A unique system of cadency is used for daughters inheriting arms, and a special symbol for United Empire Loyalists.
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In heraldry, cadency is any systematic way of distinguishing similar coats of arms belonging to members of the same family.
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During the Middle Ages, marks of cadency were used extensively by armigers in France, as can be seen in the Armorial de Gelre.
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Cadency marks may be used to identify the arms of brothers, in a system said to have been invented by John Writhe, Garter, in about 1500.
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More examples
Cadence: a recurrent rhythmical series
In heraldry, cadency is any systematic way of distinguishing similar coats of arms belonging to members of the same family. Cadency is necessary in heraldic systems in which a given design may be owned by only one person (or, in some cases, one man) at once. ...
Used of younger sons or descent from a junior branch of the family
[Heraldry] royal license by a sovereign that allows the father to grant to all the sons and their (normally) male issue the right to bear the same arms, i.e., coats of arms. Except for the eldest son, the arms are differentiated by marks of cadency.
A mark of difference to show family relationships in the system of heraldry. Included in marks of Cadency are the label (1st son), crescent, mollet, martel, annulet, fleur-de-lis, rose, cross flory, octofoil.
The distinguishing of family members entitled to the same coat of arms by a bearing; for example, the label, which is a narrow band across the top of the shield with tags pendant from it, is the mark of cadency used by the eldest son during his father's lifetime
(Ca'-den-cy) As the original object of armorial bearings was to distinguish one iron encased warrior from another, it was also necessary to provide distinctive bearings for different members of a family all entitled to bear the paternal arms. ...