What is 705 and AH stamped on gold?

The 705 stamp equates to 17 karat gold. Gold is stamped based on purity, with 24 kt gold being pure gold. 18kt gold is stamped 750 because it is 75% pure. 17kt gold is actually about 70.8% pure, but is stamped 705 instead of 708. 17 karat gold is not as common as 18kt or 14kt, but it is available. Especially in parts of Europe, Asia, and the Middle East.