Marks of Cadency

The copious manner in which your correspondent E.K. (Vol. ii., p. 221.) has answered the question as to the "when and why" of the unicorn being introduced as one of the supporters of the royal arms, induces me to think that he will readily and satisfactorily respond to an heraldic inquiry of a somewhat more intricate nature. What were the peculiar marks of cadency used by the heirs to the crown, apparent and presumptive, after the accession of the Stuarts? For example, what were the changes, if any, upon the label or file of difference used in the coat-armour of Henry, Prince of Wales, eldest…