Found near a farm field (brass and lead)?

[Henry2]

Here is a neat little piece I dug this morning near a old farm field, it appears to be lead or a pot metal with a brass cover. I have no idea what it is, any ideas?

 

[TheCannonballGuy]

Its size, construction, and emblem are typical of late-1700s through mid-1800s civilian horse-harness rosettes.