Question: what does it mean 1/20 12k?
Answer: For example – mid 20th century and later pieces are very often marked 1/20 12K Gold Filled. This means that 1/20 of the metal weight of the item consists of 12K Gold (remember that 12K gold itself is an alloy consisting of only 50% gold – thus a 1/20 12K Gold Filled item is 1/20 12K gold and 1/40 pure gold).