✅ SOLVED Cartridge ID

[Yak1366]

Overall length: 1.8"/46mm
OD just below ejection lip: 0.503"/12.8mm
Ejection lip OD: 0.596"/15.1mm

No lettering/symbols around primer.

 

[niffler]

Looks similar to the 45-70 cartridges I was digging a lot of last summer.

 

[NOLA_Ken]

not a '45-70, those are just over 2"... looks more like .45 Long Colt to me

 

[TheCannonballGuy]

In my opinion, your cartridge-casing's .509" diameter and its 1.8" length indicate it is a .50-70 rifle casing. Go to the following link, scroll a bit more than halfway down the webpage, and look at the cartridge on the far right of the four in the photo.
THE CARTRIDGE COLLECTOR

Your .50-70 casing having no "headstamp" on its base dates it to being from the 1870s into the early 1880s.

 

[pistol-pete]

Cannonballguy Nailed it