The official term for a mark of cadency is a "difference" mark, i.e. it was a mark to show the difference between one member of a family and another. The mark used to signify a lack of blood relationship, and a mark used to signify illegitimacy are each termed a "mark of distinction," i.e. a mark that shall make something plainly "distinct." What is that something? The fact that the use of the arms is not evidence of descent through which heirship can be claimed or proved. This, by the way, is a patent example of the advantage of adherence to precedent.
The inevitable conclusion is that a bastard was originally only required to mark his shield sufficiently that it should be distinctly apparent that heirship would never accrue. The arms had to be distinct from those borne by those members of the family upon whom heirship might devolve. The social position of a bastard as "belonging" to a family was pretty generally conceded, therefore he carried their arms, sufficiently marked to show he was not in the line of succession.
This being accepted, one at once understands the great variety of the marks which have been employed. These answered the purpose of distinction, and nothing more was demanded or necessary. Consequently a recapitulation of marks, of which examples can be quoted, would be largely a list of isolated instances, and as such they are useless for the purposes of deduction in any attempt to arrive at a correct conclusion as to what the ancient rules were. In brief, there were no
rules until the eighteenth, or perhaps even until the nineteenth century. The only rule was that the arms must be sufficiently marked in some way. This is borne out by the dictum of Menêstrier.
Except the label, which has been elsewhere referred to, the earliest marks of either cadency or illegitimacy for which accepted use can be found are the bend and the bordure; but the bend for the purpose of illegitimacy seems to be the earlier, and a bend superimposed over a shield remained a mark of illegitimate cadency until a comparatively late period. This bend as a difference naturally was originally depicted as a bend dexter, and as a mark of legitimate cadency is found in the arms of the younger son of Edmund Crouchback, Earl of Lancaster, before he succeeded his elder brother.
There are scores of other similar instances which a little research will show. Whether the term "left-handed marriage" is the older, and the sinister bend is derived therefrom, or whether the slang term is derived from the sinister bend, it is perhaps not necessary to inquire. But there is no doubt that from an early period the bend of cadency, when such cadency was illegitimate, is frequently met with in the sinister form. But concurrently with such usage instances are found in which the dexter bend was used for the same purpose, and it is very plainly evident that it was never at that date looked upon as a penalty, but was used merely as a distinction, or for the purpose of showing that the wearer was not the head of his house or in possession of the lordship. The territorial idea of the nature of arms, which has been alluded to in the chapter upon marks of cadency, should be borne in mind in coming to a conclusion.
Soon after the recognition of the bend as a mark of illegitimacy we come across the bordure; but there is some confusion with this, bordures of all kinds being used indiscriminately to denote both legitimate and illegitimate cadency. There are countless other forms of marking illegitimacy, and it is impossible to attempt to summarise them, and absolutely impossible to draw conclusions as to any family from marks upon its arms when this point is under discussion. To give a list of these instances would rather seem an attempt to deduce a rule or rules upon the point, so I say at once that there was no recognised mark, and any plain distinction seems to have been accepted as sufficient; and no distinction whatever was made when the illegitimate son, either from failure of legitimate issue or other reason, succeeded to the lands and honours of his father. Out of the multitude of marks, the bend, and subsequently the bend sinister, emerge as most frequently in use, and finally the bend sinister exclusively; so that it has come to be considered, and perhaps correctly as regards one period, that its use was equivalent to a mark of illegitimacy in England.
But there has always remained to the person of bastard descent the right of discarding the bastardised coat, and adopting a new coat of arms, the only requirement as to the new coat being that it shall be so distinct from the old one as not to be liable to confusion therewith. And it is a moot point whether or not a large proportion of the instances which are tabulated in most heraldic works as examples of marks of bastardy are anything whatever of the kind. My own opinion is that many are not, and that it is a mistake to so consider them; the true explanation undoubtedly in some—and outside the Royal Family probably in most—being that they are new coats of arms adopted as new coats of arms, doubtless bearing relation to the old family coat, but sufficiently distinguished therefrom to rank as new arms, and were never intended to be taken as, and never were bastardised examples of formerly existing coats. It is for this reason that I have refrained from giving any extensive list such as is to be found in most other treatises on heraldry, for all that can be said for such lists is that they are lists of the specific arms of specific bastards, which is a very different matter from a list of heraldic marks of illegitimacy.
Another objection to the long lists which most heraldic works give of early instances of marks of bastardy as data for deduction lies in the fact that most are instances of the illegitimate children of Royal personages. It is singularly unsafe to draw deductions, to be applied to the arms of others, from the Royal Arms, for these generally have laws unto themselves.