Many of the counterstamp varieties have but one certified example, and given the purpose in some cases only one example may have been created or may survive.  PCGS recognizes twenty distinct counterstamps but there are only 103 certified examples.  Six of the twenty have a single example, and three have only two examples.  Most of the certified coins are in circulated condition which seems a bit odd given that there were purchased by supporters and collectors and one might think they would have been stored away rather than carried.

In February of 2018 PCGS had certified only 12,526 Stone Mountain Half Dollars.  That is a little less than 1% of the total sold by the SMCMA.  NGC has certified another 8,895, with 112 of those being the Obverse Double Die variety, and no coin graded higher than Mint State 68.  ANACS, who certifies all double dies, has certified 2,088 of the normal die variety and none higher than Mint State 67; another 14 Obverse Double Die, 220 Reverse Double Die; and 29 with both dies doubled.

With the three primary grading services there have been just 23,772 coins graded, a mere 1.8% of those struck.