A complete collection of the 225 circulation strike gold coins of the San Francisco mint is not a collection you will be completing. The unique 1870-S $3 resides in the Harry Bass Foundation, and will likely remain there for the forseeable future. Additionally, the incredibly rare 1854-S Half Eagle, of which three are known (and only two in private hands) has not traded in over 30 years. There will be a chance over the next couple of years when the Pogue collection is sold, but expect to pony up over $2 million if you expect to land this one. Not far behind is the 1854-S Quarter Eagle, with perhaps a dozen or so known. Certified examples span the gamut from Good-4 to AU-50 with none known in Mint State. Adding four varieties (one of which is the rare 1861-S Paquet Reverse $20) to an already "impossible" set does not help matters much, and few Set Registry participants have been brave enough to try to tackle this one.