Antique jewelry pieces with a closed back most likely has set diamonds or gemstones that have foil on their reverse. This metal coating allows the diamond or gemstone to reflect more light.

No closed-back antique jewelry should be placed in water or worn engaging in any activity where water will come in contact with the gemstones. Any gap between the mount and the gemstone will let moisture in and thereby ruin the foil.

Never clean any antique or vintage jewelry with water or any other liquid. Use only a soft toothbrush to gently brush away dust or dirt. You can also use a soft cloth to clean the surface of the gemstones. Wearing antique jewelry while sleeping can effect the surface of stones over time also.

Don't leave antique jewelry in areas that are too hot or cold or in direct sun for any length of time. If repairs are needed, make sure the jeweler has a good deal of experience with antique jewelry before entrusting such pieces to their care.