In heraldry, a diamond is a lozenge
Heralds have their own word for it. The four-sided shape cut twice into this grip is a lozenge in heraldry, and for centuries unmarried women and widows displayed their arms on a lozenge rather than a shield. On this double-edged thrower the pair of diamonds is practical as well as decorative, taking weight out of the grip to balance the 20 cm knife.
