Global debt of 260 trillion, so gold has to go up around 40x for a traditional 40% backing bringing it to $60,000 an ounce and silver $1200-$3000.  Of course in a tri-metal system of gold, silver, and copper all together, you could probably lower that gold number and have a lower silver and copper price as well.  You could also have a lot of the global debt evaporate in some sort of deflationary collapse and end up with a lower gold price too.  So it will probably be a combination of all those variables and you'll end up with something like $20,000 gold $400-$1000 silver in current purchasing power.