With nothing in the picture to scale it's size by, it's hard to say for sure.
But the big ring could represent the fuse well in the nose of the bomb, the booster simulator screws into that, then the fuse simulator screws into that.
I was a USAF munitions specialist in the late 60's, we did have dummy (inert) boosters and fuses, but they looked like the real thing,
But that could be from another countries munitions, but I've never seen anything like it.
When I went thru munitions school we practiced with inert components, full size, but other countries might have done it different.