What is this Bakelite disk for?

[Anders]

I only have the photos and no additional information. The two half are glued together.

 

[batonroundcollector]

A guess, but maybe a US-produced training item to represent a foreign mine; I don't recognise type (which may or may not be bakelite itself) it is supposed to depict though...

 

[Anders]

I had some x-ray taken and had it measured, not that I am any the wiser.

 

[Bombdoc]

I think it may be the bung for a 120 Challenger cart case..

 

[Anders]

I think it may be the bung for a 120 Challenger cart case..

Can you elaborate on this?