I forget exactly why but I think it was because they were all recalled when we went off gold standard?
I vaguely remember people finding these in deposit boxes, sharing it with the news and then magically losing it all when the treasury shows up to seize them.
Ah here we go
http://en.wikipedia.org/wiki/Executive_Order_6102
not really related but still gold-coin mind-blowing fact
http://www.npr.org/2011/06/28/137394348/-1-billion-that-nobo...