Check for hallmarks or stamps such as 10K, 14K, 18K, 22K, 24K
Use a magnet to see if it is attracted
Look for discoloration, flaking, or worn plating
Rub it on an unglazed ceramic plate and inspect the streak
Test with a gold testing acid kit
Use a digital gold tester
Weigh it and compare with known gold density
Check for a hallmark from a reputable jeweler or assay office
Have it tested by a professional jeweler or pawn shop
Use an XRF analyzer for precise metal composition testing