This is going to be a wild guessing game. It appears to be a decorative washer, If it had only one hole in the center of a star, and if the star was thicker in the center than the edges, I would say it was a washer for a tension member of a load bearing brick wall in a building.

Old buildings with load bearing, brick walls, had a nasty habit of suddently collasping, The load bearing wall would buckle outward and dump the load, in this case, the rest of the building supported by the eall. About 100 yrs ago, builders began installing tension rods across the width of the buildings between the floor joists of the second floor. This was done to tie the two walls together to resist a suddent collaspe from buckling. Evidence of this construction can be seen on the outside of the building. Look up at the second floor level on the brick wall and you may see large decorative washers with the end of a threaded rod sticking through it with a large nut. These are the tension rods.

I know of one store building in Flora, IL that had a load bearing brick wall and it collasped without warning. Few occupants were inside at the time and they escapes injury by ducking down. The grocery shelving supported the falling upper floor and provided an escape space. There is another very old store building in the neighboring town of Clay City, IL and it has the tension rods described above.

Your plate reminds me of a decorative washer similar to foregoing discussion, but I would expect only one hole and a greater thickness in the center. I think that you piece is a decorative washer, but I don't know where it could have been used. It may have been part of machinery, or a building.

My old house has two of those rods, but the bolt is huge, any washer used on it would be much larger than this. The two holes are likely screw holes, and I don't have a clue to what, either. This was a very old farm, and we find things like this often, and sometimes away from the house proper because folks just dumped stuff in piles when they were done with it.

I also suspect it may have been part of machinery. Like a cover to a working mechnism or oil hole. It could also have served a strictly ornamental function, like decoration on horse tack.

Commanderklank, There is a web forum for things people find underground. Things from the Civil War . They might be able to help identify your item. Here is the site

http://forum.treasurenet.com/index.php