If this is just about rings, then I cannot see how they have borders or trimmings, which might be the usual way of translating the Besatz bit. I wonder if you could give a sample sentence in which this term is used, please?
http://www.jewelry.com/education-diamond-settings.shtml

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Note added at 3 hrs (2009-02-17 12:04:41 GMT)
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Yes, given the context, for me it is 'stone setting' that you need: 'crowned with an exclusive stone setting'

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Note added at 3 hrs (2009-02-17 12:14:15 GMT)
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You could also use 'gem setting' which is also often employed.

There are several types of diamond jewelry available at De Beers boutiques. While the most popular collection is the bridal selection, including engagement and wedding rings, other types include:

Eternity Rings: Channel and prong settings are available, including a unique knife-edge design using two angled rows of stones. Round and princess cuts are the most popular diamond shapes.
Men’s Rings: A limited selection of men’s fashion and wedding rings are available.
Three Stone Rings: Bezel and prong settings are the most popular, and stones may be graduated or matched in size.
Exclusive Collections: A variety of earrings, bracelets, and necklaces are available in a wide range of styles, including figural pieces, right hand rings, pendants, cuff links, and more. Some collections even featured colored diamonds and unique shades of gold.
De Beers 3/4 Carat Solitaire[edit]De Beers Engagement Rings
An engagement ring may be the first or only piece of diamond jewelry a woman owns, and a ring from this exclusive designer is one that will reflect her love and commitment in its perfection. There are a variety of designs available, and solitaires are by far the most popular choice. Several fancy shapes are available, including emerald and princess cuts, either alone or paired with complementary accent stones. Pave settings are popular, as is the exclusive Trident design – a round stone in a unique triple prong setting that allows the maximum amount of light to enter the gem.

Engagement rings may be set in platinum, yellow gold, or white gold, and many designs are planned to match the simple wedding bands the designer offers
http://engagementrings.lovetoknow.com/wiki/De_Beers

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Note added at 3 hrs (2009-02-17 12:18:15 GMT)
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http://www.asia-gems.com/jewelry/settings.php

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Note added at 3 days2 hrs (2009-02-20 10:31:39 GMT) Post-grading
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Thanks for the points, David