I recognize that I'm replying to an older thread, but I just recently joined this forum and am just now discovering threads related to my primary area of interest - US commemorative coins. So, I thought I'd respond to a few of the questions/comments I read...
"...these coins are going to be worth a lot more in the coming years." (Representative comment echoed multiple times.)
I would not assume that they are going to become highly valuable in the future. There are over 1 million of them available to collectors and souvenir hunters - that's quite a few coins! I agree that higher grade examples will likely show price advances, but lower grade examples are plentiful. Stone Mountain half dollars are a common sight at coin shows - in a range of grades - and are always available for purchase. Folks at estate sales sometimes pay way too much for the coin because they mistakenly think it is rare - it's wasn't rare back in the 1920s, it's not rare today and it won't be rare in the future. My advice - review online auction sites and learn more about selling prices (not asking prices!) across the various conditions/grades before putting your money down for one and possibly overpaying!
"I'm sure it's in the fine print somewhere but how many actually made it to circulation? Or did any?"
No exact figure is known for exactly how many of the Stone Mountain half dollars entered circulation as standard US half dollars. During the time when the coins were being actively promoted (mid-1920s), a number of banks purchased significant quantities to support the Memorial effort and for their own promotional use. Many of these coins, however, were not sold or distributed and remained in bank vaults into the 1930s. It was during that time frame that the greatest number of the coins these "leftover" coins were released into circulation at face value vs. being sold at a premium. (The coins were originally sold for $1.00 each.) The US Mint did not drop any bulk groups of the coin into circulation; it melted those that were returned to it by their sponsor.
"I am wondering how prevalent they are among collectors, and especially with estate sales, and other market places."
The Stone Mountain half dollar is popular among a segment of coin collectors, but not necessarily across all collectors. Among those collectors who specialize in US commemorative coins, the coin is popular. It is needed if: 1) a collector is assembling a topical set of Civil War-themed coins; 2) if a collector is looking to collect one of each design type of US commemorative coin issued between 1892 and 1954 (50 coins are required); 3) if a collector desires to assemble a complete 144-piece set of the early US silver commemorative coins; 4) if a collector is assembling a topical set of coins with horses (or animals); or any one of many other topical sets. There are many examples of the coin in the marketplace, however, so there's plenty to go around!