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One of the challenges to appraising jewelry is dating an item – called circa dating. Over time, gemologist-appraisers have learned the styles associated with antique and period jewelry. Certain gems may have been introduced to the trade at specific dates. Cutting styles also change and add to the ability to circa date an item. Circa dating improves with each new discovery and diamond cut styles are a key element.

When did they cut old mine cuts? When did they cut old European cuts? These time periods help to circa date a vintage piece.1 A source for dates is researching public records. To read a published court case, for example, that describes a circa dating element is a remarkable discovery. Another resource are patents.

In my endeavor to add plotting diagrams to Perfect Diagram,2 I have been researching patents. There are numerous patents for cutting yet to be reviewed and added to the gallery, but this is not an article about Perfect Diagram. It is about discovering a new circa dating element.

A Patent from the Past

1904 Patent

While researching patents for diagrams, a United States patent, numbered 809,531 was filed in May 3, 1904 and granted in January 9, 1906 to E. G. H. Schenck. The patent was for polishing a round brilliant diamond’s girdle! This, I learned by further research was also documented in Al Gilbertson’s book.3 Al’s book states that prior to this patent, girdles were rough or unpolished.

1941 Patent

What can we learn from the patent? A polished girdle was to add brilliancy as well as strength, especially when setting the diamond. The patent pointed out that a polished girdle would “… lessen the liability of chipping …” and “… may also add to the brilliancy of the stone.”

And, in tandem with Al Gilbertson’s book, if a diamond has a polished girdle – we can assume that it most likely fashioned after 1904. The cut style, especially when observing the diamond’s pavilion, will fine-tune the circa date.

Another Patent from the Past

1904 Patent

In my research for cuts to add to Perfect Diagram, I also discovered a second United States patent, numbered 2,340,659 that was filed in May 5, 1943 and granted in February 1, 1944 to Edward Goldstein. The patent was for faceting a round brilliant diamond’s girdle!4 In contrast to the 1904 patent, I found no mention of it in any of my library or online resources.

What Did We Learn from the Patent?

1941 Patent

The faceted girdle was to add brilliance to the diamond. The patent explains that a faceted girdle “… relates to a novel arrangement of facet surfaces whereby, among other valuable features, an improvement in brilliancy …”

The girdle was to have at least a recommended additional forty facets. “A brilliant-cut5 precious stone having a faceted crown and a faceted pavilion with a girdle interposed between the crown and pavilion, the girdle comprising forty or more facets which slope upwardly and inwardly, the inclination of the girdle being between 10° and 30° from the vertical.”

This patent’s description and illustrations reveal that a top view would show a slight amount of the faceted girdle.

Thus, if a diamond has a faceted girdle that is slightly visible from a top view – it is most likely this patented cut style. And, lastly, we can assume that a diamond with a faceted girdle most likely was fashioned after 1943.6 The cut style, especially when observing the pavilion’s cut style, will fine-tune the circa date.

1. See The Ongoing Debate over Old Cuts for more information.    Back to Text ↑ ↑ ↑
2. A gallery of precision cut diagrams used for plotting gemstones. See Perfect Diagram for more information.    Back to Text ↑ ↑ ↑
3. American Cut the First 100 Years, by Al Gilbertson, page 183.    Back to Text ↑ ↑ ↑
4. A non-design patent was also filed by Mr. Goldstein, patent number 137,163, filed May 5, 1943 and granted February 1, 1944. The patents are duplicates.    Back to Text ↑ ↑ ↑
5. There is some discussion as to what to call the transition cuts, but the one illustrated in the patent was called a brilliant-cut. See Identifying and Valuing Old European Cut Diamonds, by Richard B. Drucker, published in July-August 2019 issue of Gemguide.    Back to Text ↑ ↑ ↑
6. Although there may have been diamonds with faceted girdles before 1943, one can rely on the published date from the patent as a defendable circa date.    Back to Text ↑ ↑ ↑

Respectfully submitted,

Bill Hoefer

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