Vintage Necklace 18" with Red Crystal Ball

I have owned this for 60 years. The chain is not stamped. It is a gold colour.The chain measures 18 inches long and is 2mm wide. The chain weights 2.8 grams. The crystal ball is floating within the setting. The crystal measures 10mm. This item has been polished, as it is not gold or plated gold it will return within time to a patina.