I have a puzzle for you; bought a very nice 5 ounce Silver coin from 2005 with St George and the Dragon on one side. The seller says it is pure 999 silver, but the certificate says it is 925 silver. The weight of the coin is 157,7 grams On the bottom of the coin are four stamps or hallmarks; the first is a SN? the second a 999; don't know what this means 999 silver? the third a scale with 925 in it; which means it is 925 silver the fourth a dog with a Z in it; which states that the coin is made in Zurich Zwitzerland Who can help me with this one? what does the hallmarks SN and 999 on the coin mean?