"Empty" 3 inch mortar bomb

[Infanteer]

Here is my collection of 3 inch bombs. My question is about the bomb marked "Empty". The top is painted green and has a red band. Can someone tell me about this bomb?

 

[25thapril]

Could it be a class room instructional piece ???

 

[Infanteer]

Perhaps.... like a training "dummy" bomb as opposed to an inert practice bomb intended to actually be fired. That would make sense. The markings are not standard though. The red band is the normal width but the green section is huge compared to what is normally seen.