Who is Anton Antonych Setochkin from Notes from the Underground and what is their importance?

Anton Antonych Setochkin is the writer's office chief. He is described as "serious", but the writer goes to him to borrow money for a beaver collar for his coat in order to present a better appearance upon his meeting with the officer. Anton is said to be the only "lasting acquaintance" of the writer. When the writer is planning to challenge Zverkov to a duel, he believes he'll ask Anton to be his second.