Rifle cartridge?

[normalizer]

I found this Sunday on a field about 4 miles from the CW battle of Thompson Station, TN.

I immediately thought it was a cartridge but there's no primer, unless its a rim fire.

No visible markings anywhere in it, appears to be brass/copper with its green patina.

Photo taken with penny for scale.

Any guesses?

 

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[TheCannonballGuy]

It does appear to be a rimfire bullet-casing. Need precise (hundredths-of-an-inch) measurement of the casing's flat base, and also the dimater of the casing about 1/8" above the flat base, for certainty about what caliber it is. At the moment, it looks like a civil war .52-caliber yankee Spencer Repeating Rifle/Carbine casing.