I found this near an old farmers co-op builiding in Florida. It is 2 1/2 inches long, and 5/8 across the base. the actual bullet seems about 3/4 but its hard to tell because of corosion. it has no headstamp other that an indention of an "x" in the center.
I see that is your first T-Net post, so, welcome to TreasureNet's "What-Is-It?" forum, the best place on the internet to get unknown objects CORRECTLY identified.
Your photo of the cartridge's base is too blurry, but since you say it has an indented X in the center, I'll combine it with the measurements you provided. It is a Swiss .41-caliber Vetterli Rifle cartridge, dating from 1869 through about 1890. Many were sold as army-surplus to American and Canadian civilians for game-hunting. The "indented X" is actually the Swiss Cross, and it means your cartridge is Swiss-made. See photo below.