User blog comment:FallenShadow/Fallen's Reviews: Chapter 341-343/@comment-86.66.207.93-20130713091728/@comment-7418318-20130713125125

Considering that we already got the gold and black key of Ophichius, I wouldn't be all that surprised if other keys that are not tied to the 88 constellations of Uranometria would have a similar look.

Platin would be a bit hard to differentiate from the silver keys, depending on the ambient light.

And I think the english version is "Cerberus" with the original greek name being "Kerberos".