Maybe they are not so rare - I found another King George III - VA Half Penny today - 1773. It was at a different site than the first one I found in January. Still very exciting to pull it out of the ground. Here is the link to my other thread if you need a photo reference, as today's coin is soaking in olive oil. 
http://www.findmall.com/read.php?79,1608687,1608701#msg-1608701

http://www.findmall.com/read.php?79,1608687,1608701#msg-1608701
It's kind of senseless that so many relics remain buried to be lost to the dirt gods rather than being allowed to be recovered for everybody to enjoy and learn from. I understand the battle site reasoining, but not so much with regular pieces of ground in the VA area. Our country is losing so much physical history every day by keeping it in the ground and letting it ruin.