78Pt The 3, 6, and 12 Ruble coins of 1828-1845 were the only Platinum coins ever minted for circulation. They are made from granules of native "pure Ural platinum" ore, sintered because the melting point of Pt is so high that casting ingots was technically unfeasable at that time. Thus these coins have a rather odd, porous surface texture and are less dense than pure platinum. PCGS certified. (JM15)