It is a penannular kilt pin.
Originally worn by Romans as a brooch to secure cloaks, they were adopted by Scots and Irish to secure Kilts and, continue in use today.

I dont remember. .But I found alot of King George's at that site also..So who knows..
The penannular kilt brooch gets my vote. Here are some variations ...
<img src="http://www.treasurenet.com/forums/attachment.php?attachmentid=1046601"/>
http://s183.photobucket.com/user/JohnSenWint/media/KiltBrooch_zps85cd548e.jpg.html
gets you these wonderful old relics. Congrats yet again on an awesome find. Was this from your 1800's farm site you just hunted? With the Philadelphia area's worldly history, it does not surprise me to find items from any nation.