Vintage petite 1/20th 12K GF cross necklace Measures 16 5/8” Cross measures 7/8” Entire piece weighs 1.42g (.050 oz). An item marked 1/20th 12K GF (gold filled) has a layer of gold over a base metal that equates to 1/20th of the weight of the entire item. This means that a piece stamped 1/20th 12K GF and weighing 1 ounce, contains 1/20th of an ounce of 12K gold. It takes about 40 ounces of 12K gold filled metal to make one ounce of pure gold.