Koi Types
Nezu Ogon
Nezu Ogon are an old type of Ogon. They are a metallic
colored dark grey Koi. As with other
Ogons, the color should be uniform
throughout the fish. Also, look for any signs of previous
damage, for any
scars will take away from any Ogon's look.

Helmet Head?
Nezu Ogons have a dark area on the center of their heads. This has caused
many
breeders and Koi keepers to affectionatly nickname them Helmet Head.
The dark
area almost looks like a maruten spot, but is it usually not very
uniform in
color and does not have sharp edges.