This blue stock certificate from Lazare Kaplan International (LKI), issued in 1977, features a beautiful vignette of a diamond, along with cancellation holes, stamps, and handwritten annotations, indicating its authenticity and historical use.

Lazare Kaplan International was founded in 1903 in New York by Lazare Kaplan. The company is renowned for its expertise in diamond cutting and polishing. In 1984, the Tempelsman Group purchased a controlling interest in LKI. LKI has been publicly listed since 1972, making it the only diamond manufacturing company with shares publicly listed on a US stock exchange, specifically the American Stock Exchange under the symbol LKI. LKI has been a Diamond Trading Company (DTC) Sightholder since 1946 and, in 1985, became the first company to launch a branded diamond, known as The Lazare Diamond.

The company's innovation history is marked by significant contributions to diamond cutting techniques. In 1919, Lazare Kaplan's cousin, Marcel Tolkowsky, published the mathematical formula for diamonds cut to "ideal" proportions, optimizing brilliance, fire, and sparkle. LKI was the first commercial-scale operation to cut diamonds to these ideal proportions. In 1957, the company developed the modern oval cut and, in 1983, patented the laser inscription process. In 2002, LKI was awarded a patent with General Electric for the high-pressure high-temperature (HPHT) process to improve the color of certain natural diamond types.

Today, LKI specializes in cutting and polishing "ideal-cut" and "fine make" diamonds, selling them to upscale retail jewelers worldwide. Their products are distributed through over 1,500 retail partners and customers in 29 countries, with operations based primarily in the United States and sales offices in Belgium, Japan, China, and Hong Kong.

LKI's first factory was in Ponce, Puerto Rico, the largest diamond cutting and polishing facility in the United States. The company also has manufacturing operations in Russia through a partnership with Alrosa, and contract manufacturing in China, Thailand, Botswana, and Namibia.

In recent history, Lazare Kaplan faced legal and financial challenges. On May 17, 2010, the company sued various Lloyd's of London syndicates and European insurers for $640 million in damages related to the disappearance of diamonds. Since September 2009, LKI has been suspended from trading on the American Stock Exchange and has not filed quarterly or annual reports with the SEC since early 2009.