Whoops, didn't catch that measurement.
However, look at the construction of it. it is just like a Haiden Horn....
The leather megaphones I have seen don't typically have the bar across the center, they are generally smooth leather and have a reinforced mouth area that is leather/metal/brass, etc.
I have only seen one listed as a megaphone (currently on ebay) that is similar construction and has similar inner construction. Don't believe it is...