Special-Colored Pure Black Blade Broads?

Does anyone know if there was a special-colored version of a broadsword with a pure black blade? I remember picking up two of them from someone's store for 50k each about a year ago. I assumed the swords were completely identical and cheap because they came from some gacha.

I have several black Broadswords that I bought a long time ago, but I don't know where they originally came from. And if it came from an event or gachapon, there's no pages that say so.

Might have just been from an npc shop. They sometimes sell black bladed weapons.