No understudy latch here. A double latch clasp gives both locking points equal billing, unlike a box clasp with safety where the catch backs up the main box lock.
Stone Story
Cubic zirconia and crystal glass are not the same material or the same performance tier. CZ has a significantly higher refractive index and hardness than leaded crystal glass. It produces more brilliance, resists scratching more effectively, and holds its surface quality over time.
Visually Speaking
The flat housing surface of a box clasp lends itself to decorative work. Whether it be engraving, stone setting, or milgrain edging, the result is a closure that contributes to the piece's overall composition rather than just simply finishing it.