looks like a fragment of the reeded edge sheared off when the coin was in the collar between strikes, too, as part of the fragment is retained within the edge itself....
you could send the photos in an email fo Fred Weinberg at this webpage and see what he has to say. http://fredweinberg.com/
I think you have a fairly neat error there BUT, it's been my experience that uncommon error's may not always interest error dealers that deal with off-center, broadstruck, incomplete planchet and double struck coins. Errors such as what you have found need to be "marketed" to the appropriate audience for the coin to realize any significant premium. Someone, somewhere will want your coin but its all about finding that person. Finding two people that want it will drive the price up. Personally, I like the coin and find it unusual as a proof piece but I, admittedly, know very little about these. Fred Weinberg may be able to give you a more realistic value since all he deals with is error coins and he has a very broad customer base. Good Luck!
Thanks for all the advice on this matter. I've learned a lot of new information in the last week and I'm better for it so that is the most valuable part of this. I've decided to go fishing with the coin and doing a "eBay appraisal" by putting it up with a high reserve. ebay listing After that is done I will decide who I might send it in to.