Karat stamped gold jewelry sold in the U.S. must have the manufacturer's trademark. This is known as the hallmark and is required to be there by law. If there is a hallmark, the manufacturer guarantees the accuracy of the karat mark. The country of origin may also be shown.
Check the clasp to make sure it is strong enough to support the chain, especially if there is no hallmark. Feel the chain for rough edges. Quality gold jewelry should be comfortable to wear.
The price of gold jewelry is determined by several factors: karats, weight, design, construction and ornamental detailing like engraving and finish. Most gold jewelry today is created using special machines with some handwork involved.
The more handwork there is, the higher the price. Because of modern manufacturing techniques, large, lightweight, and beautiful pieces are more affordable.