That is a copy of the 'Kornburg Helm' housed at the Germanisches Nationalmuseum in Nuremburg, Germany.
Here's a photo of the original helm. The real helmet's ocular is painted that latten color, it's not brass or bronze, and the paint is not thought to be original. The mini-aventail hanging from it is also not thought to be original. It's dated to the mid 14th century. It's a cool looking helm!