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