In the 1940s, after the second World War, GIs stationed in Japan discovered the beauty of cultured akoya pearls. They bought and brought home thousands of strands of pearls that almost all had one thing in common: They were graduated.
A strand of pearls of decent size would have been financially unattainable for most, so Japanese pearl dealers created graduated strands. These strands were described by their momme weight, the most popular of which was the 3.5 momme strand. There were also 5 momme and 7 momme strands, which were too expensive for most GIs, so very few of them found their way back to the United States.
This is a 5-momme strand of pearls. The pearls graduate from four to just over eight millimeters and the necklace is nearly 20 inches in length.