The blade itself mimics the shape of number 1200. Human Age. Unusually, the blade and hilt are not attached and it floats. Upon being activated, the blade and guard area disassembles and splits apart. Roman numeral MCC is engraved on the blade near the point.
In the process of being delivered to Anne by Admiral Jack Norton, it was fired from the Alcyone's railgun. Norton comments that "this is the most expensive and strongest bullet in the whole universe!!" Thanks to its own anti-barrier effect, which is so powerful that it can't be compared to normal AB Swords, and it's prodigious kinetic energy, it pierces right through an entire Blue Flower and lands on the surface of planet Arin.
It seems as though Norton had locked onto A-10's beacon when aiming for the surface of the planet, as Number 1200. Key Sword landed right in front of her. A-10 then personally brings it to Anne just in the nick of time.