An amorphous metal is a solid metallic alloy material that exhibits an unusual atomic-scale structure compared to all other metals. Amorphous metals are produced by several differing procedures, all of which are complex and require specialized equipment and trained personnel. The first successful production of an amorphous metal (also known as metallic glass) occurred at Caltech in 1960. The positive quality is its high coefficient of restitution (COR). This measure of the “restitution” of a collision between two objects and how much kinetic energy remains for the objects to rebound makes the material ideal for manufacturing thin-faced golf club heads and golf balls.