Papworth's has both what's the diefference ? Arg. 3 man's hearts ppr. Gu. on a fess arg. 3 men's hearts gu.
This is just a particularly attention-grabbing example of a broader controversy in blazoning. If one of something is a "lion's head," some argue that two of them are "two lion's heads," while others contend that (putting aside the existence in heraldry of two-headed lions) it must correctly be "two lions' heads." The difference is purely pedantic, not heraldic.
By the way, why don't we stop the silly practice of blazoning the conventional heart in heraldry (the one that looks like a playing card heart) as a "man's heart" or "human heart?" Would anyone emblazon "Arg. 3 hearts Gu." any differently than "Arg. 3 man's/men's/human hearts Gu."? It actually looks more like a violet leaf than it does a human or any other heart.
Joseph McMillan