American Army Mystery Item ????????

[macs1]

Please can anyone help us identify this cast iron object found in the same spot as American spent cartridges?
Thank you
Macs

 

[releventchair]

Some old coal stoves used to have a kidney shaped reservoir to add humidity. I think the one I used that had been converted to gas (an interesting conversion , but effective) had a lid. Must have had a way for humidity to enter the single plenum above the firebox from the reservoir.

Not saying that is what your piece is.