I think if you look at the way the Guy is balanced the bomb or casing is more or less wedged where it is. Otherwise l think he would fall backwards, though of course the photo only catches a moment in time and perhaps the guy fell flat on his back moments later.
I am certain the bomb is a bomb 1) because of its shape. 2)bombs tend to be described by weight, naval shells by calibre. 3) The location does not support the idea of it being a naval munition as all the fighting was away from the USA so almost all munitions needs shipping anyway. The hoops around the casing were to do with handling and removed before final use. The bombs are not fused and probably also lack tail fins. Did the US export empty casings for the British to fill when they got to the UK? In the first world war the British had shell filling factories, presumably filling cases cast, and manufactured elsewhere.
