A cursory consideration of medieval coats of arms shows that any of them might undergo variation, often marked, without obscuring its association with the bearer and his family. Anyone who recognizes that a barry of argent and azure stands for Grey is prepared to allow that the same arms with a bend or a label or three roundels added may quite possibly indicate another Grey kin to the first. It is to such variants as these three latter examples that the technical term ‘differencing’ is here applied, that is, modified versions of an original arms borne by several members of the same male stock. While every student is aware of the fact of this differencing, the number of ways, or modes, of it is unexpectedly large. The following lines indicate the principal modes that are exemplified by the early rolls of arms still extant. Every discernible example—some thousands—has been examined.