"Nelson is extremely obese, to the point where he is unable to walk and must be carried on a humongous chair, by at least six men. This also prevents him from being able to wear a fitted marine coat, which can only cover his arms and back. On his huge stomach, he also has a large tattoo of the Marine emblem in blue.

He, aside from his extreme obesity, has some other peculiar marks. He has a long, thin, curved moustache; spiral marks on his huge cheeks and he also seems to have no eyebrows, having two dark spots in their place instead. He also wears a rather expensive looking gold necklace with a red gemstone embedded in it.

On his head, he wears a tall blue marine hat which is also unique in that no similar marine hat was ever seen before or after."

(Source: One Piece Wikia)