Thank you for the picture of your Quahog pearl, Dennis. It is indeed an incredibly special pearl. You are a member of a very elite club!
This is a link to a page dating back to 2003. Several people who read about the Quahog pearl brooch wrote to a forum to mention their own Quahog pearls:
http://www.cronaca.com/archives/000821.html
Unfortunately, there are no pictures of those folks' pearls. I hope some of them find this forum and send photos.