PCGS actually assigns these a catalog number and lists them in their population report for every counterstrike. If you look at their web site you can see them. The number that have graded is very small, less than 200, and there are some interesting twists. (Yours is probably 525162 ( https://www.pcgs.com/pop/detail.aspx?c=789 ) In the sales effort the Commission marked some with SL and others with GL in addition to the state and number. This stood for Silver Lavalier and Gold Lavalier, or levels of sales awards. Many of these coins are considered damaged by PCGS because they are usually in a bezel or have a soldered loop attached. The state and number were used to create interest and many of the coins were sold at auction to drum up sales for the cost of the memorial. At least half of the ones I have researched have N graded because of some overstrike problem, bezel, or just damage. So the number of actual graded coins is very rare even though many were counterstamped. I am looking for a publication done years ago that is probably the counterstamp Bible, but so far it has eluded me.