From the movie Mad Max: Fury Road, this item is inspired by and resembles the one of the toothed gears worn by the film's main antagonist, Immortan Joe. There is very little reference imagery available of this particular piece beyond a select few scenes from the movie. However, I did my best at eyeballing the general shape and dimensions, and I think this is a pretty clear representation of the part.
This is not a functioning gear and should not be used for those purposes. It is for decorative use only.