Since you said you also found medicine bottles, could it be a seal for the medicine, similar to this modern one?

Let us help you identify that mysterious object you’ve found.
Currently in CHALLENGE mode: If you've got something obscure knocking about, post a picture, and let's see how we do. Please prefix such posts with "CHALLENGE:" so we know we've got a fighting chance.
Since you said you also found medicine bottles, could it be a seal for the medicine, similar to this modern one?

What sort of scale are we looking at here? To me, the raised perimeter and hole in the center looked like an old chevy tie rod end, but it would have to be in a severe state of decay.

Looks to me like an old fuse end cap. Similar to one of these fuses
Whats the outer diameter of the circular end? And the inner diameter for the little hole in the middle?
Just from eyeing it, looks to be about 30mm and 5mm.

Underside. You can see in the center (both sides) that it looks like there is a hole going through it.
Edit: changed hold to hole... Autocorrect issue.
Where abouts was it found like country wise and does a magnet stick to it.
US, in Georgia and yes magnet does stick to it.
Well it does look a bit like civil war era rifled artillery shot. Look into your cities history during the war.
Ed: I don't necessarily think it's that exact shot but the right image is to clarify why I think it might be especially with the sides splayed or like that.
http://www.civilwarartillery.com/
The link resets back to the homepage. It's field projectiles, rifled projectiles read-parrott and at the top there is one that says read v parrott and it'll be the image on the right.
This makes sense, especially for the area that I'm in right now.
If you haven't already get a gps tag so you have lat/long coordinates and take it to your local museum. Chances are they'll have a fairly detailed list of what went on there artillery wise and between location, size and shape they should be able to narrow it down.
That's a really good idea. I'm only here for a few more days but I should be able to get in contact with some of the local places for info.
It looks like it snapped off of something larger. Is that dirt in the middle or a completely rusted bolt? I’m curious whether there’s threading at the center beneath the brown.
My first thought was to stick it in acid to get a better look tomorrow, until I read “1800’s - early 1900’s”
I brushed it off with a nylon brush since the other things that were found seem to indicate that it may be quite old. I do think the center is hollow but I'm trying to be cautious with it.
My first thoughts were an ols zinc acid cell (battery), but not really sure what it is
From the top it looks like a skate barring, but i dont know how it got so junked up? Im probably wrong.
Are the edges rubber? Looks like a piston from a bike pump.
Some kind of metal, brass or something else. The whole bottom side seems to be of a similar material.