This is not the standard used in the US. You will find that other countries use a different standard.
This is the information from the company that I buy from:What is gold-filled jewelry? Gold-filled jewelry, also known as "rolled gold", is composed of a solid layer of gold that is bonded with heat and pressure to another metal. Our high quality gold-filled jewelry has the same appearance as solid 9k gold, and is far more durable than gold plate,even with daily wear,And our nickel-free 9k gold-filled jewelry is a perfect solution for people with sensitive skin. If you can wear solid gold, it is highly unlikely that gold-filled jewelry will cause irritation.
Nickel free-Gold Filled/Gold Layered Jewelry(the highest Safey Standard & environmental protection standard ), Our 9k gold filled jewelries are guaranteed to not irritate sensitive skin.
Go to https://www.listia.com/account/verify & it will explain it all to you. It is very easy to do & you will need it to buy & sell. Many buyers won't buy & many sellers won't sell to someone who is not Listia verified. It just makes the transaction safer.