Stanhope (optical bijou)

A stanhope, or stanho-scope, is an optical device invented by René Dagron in 1857 that allows for the viewing of microphotographs without a microscope. Dagron's innovation involved mounting microphotographs at the end of a modified Stanhope lens, which he called bijoux photo-microscopiques. Prior to this, microphotographs created by John Benjamin Dancer in 1851 required a microscope for viewing, making them less accessible. Dagron's design enabled magnification of up to 300 times, allowing the microphotographs to be incorporated into various miniature artifacts, such as jewelry and toys.

Dagron's viewers gained popularity after their introduction at the 1859 International Fair in Paris, leading to the establishment of a dedicated factory for their production. By 1862, Dagron's factory was producing 12,000 units daily, and he developed mail order marketing techniques. His work was recognized at international exhibitions, including an "Honourable Mention" at the 1862 International Exhibition in London.

In the early 20th century, Eugène Reymond took over Dagron's factory, which continued operations until 1972. Although traditional methods ceased with the factory's closure in 1998, stanhopes are still produced today, primarily as gold or silver crosses featuring Christian prayers in the microphotographs. The stanhope remains a notable example of innovative optical technology from the 19th century.