Mystery brass item

[zbrown210]

So I found this mystery brass item at a civil war site and the thing that made me curious to what it is, is it appears to have a large caliber bullet hole to it. So I lugged it several miles with the hope that one of y'all might know what it is?

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[fyrffytr1]

Are you sure it is brass and not copper, maybe? Could it be a part of an old battery?