Your diamond's certificate number (or jeweler's designation) can be laser-inscribed on the side of the stone, allowing it to be positively identified in case of theft or after cleaning or repair. Such inscriptions, which are visible under magnification (shown at right for the ring below) don't affect the gem's value. They cost from $40 to $200 and offer more than mere peace of mind: Some insurance carriers will give policy discounts on inscribed diamonds.

1.9-carat round diamond in platinum with pave diamond accents, Hearts on Fire, $66,485; 877-737-3328.