So John Howard, the Duke of Norfolk wears the wrong livery? It now seems that he is the eldest son of the King of England, which he is not of course. I wonder why Osprey did this...
As fas as I know the label just denotes any eldest son - not necessarily the eldest son of the King.

There is more info on it at the site, which Desiderata has given abve.
Nice links, especially the middle one. I have bookmarked them


The label resembles the strap with pendants hanging down, that was worn across a horse's chest. It usually has three or five pendants - these pieces can be straight or splayed, or in dovetail form. (this is up to the individual heraldic artist and isn't specified in the blazon). It is usually used as a mark of cadency (see Part Ten) which is borne by an eldest son on his arms, while his father is still alive. Labels can be drawn in several different ways, for example the strap at the top does not have to extend across the whole shield. Which type is used is up to the heraldic artist and is not specified in the blazon