Silver-filled is a new layered metal, introduced during the surge of silver prices during the recession. It is not an alloy because the metal content is not the same throughout the material. Silver filled is either 5% o 10% sterling silver by weight, fused with heat and pressure to a brass core. Since silver-filled is a layered metal it cannot be cast. The silver layer thicker than silver plated, but this is still a much lower quality product than most solid silver alloys. Now that the price of silver has gone down, this metal is less common in the market. There is no legally approved quality stamp standard for silver-filled pieces at this time.