A Dutch silver microscope by Antoni van Leeuwenhoek, c.1690, that sold for £260,000 at Christie’s South Kensington. The size is deceptive, the main plates measure only 11/2in (4cm) long.

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Using his own simple instruments, it was Van Leeuwenhoek who first observed such wonders as muscle fibres, red blood corpuscles, bacteria, protozoa and spermatozoa - which he called "little men".

Accounts vary as to his career path, but he seems to have worked as a surveyor, a beer and wine gauger, a minor civil servant and as an apprentice to a cloth merchant, where he learnt to examine fabrics with a magnifying glass. At some point he was to learn how to grind and blow lenses and in 1671 had constructed the microscope that would open a way into the world of micro-organisms.

It was relatively simple - two lenses held between riveted silver plates - but focusing was achieved by a screw mechanism.

Given his lack of a formal education, his claims were at first dismissed as fanciful. However, a letter announcing his discoveries of animacules, or "little animals", living in rainwater, was eventually translated into English and published in the Royal Society's Philosophical Transactions. He was elected a Fellow in 1680.

Van Leeuwenhoek would present his microscopes to Queen Mary and to Peter the Great, and gave 26 silver examples to the Royal Society - all now lost. In all, he is thought to have made some 550 microscopes, mostly in brass, though very few seem to have survived.

The appearance of a silver example in a mixed book, picture, print and scientific instrument sale at Christie's South Kensington on April 8 was thus a very special event.

Just nine 17th century Van Leeuwenhoek microscopes are now recorded, and only three of them are in silver. One is in the Deutsches Museum in Munich, another in the Boerhaave Museum in Leiden, while the example at South Kensington was found in a box of laboratory impedimenta from the Zoological Department of Leiden University in 1978, when it was purchased around that time by the vendor.

Reproductions of Van Leeuwenhoek instruments were made in the 1880s (the example in the Carl Zeiss collections at Jena is believed to be a copy), but potential buyers at Christie's were reassured by the presence of two 19th century Dutch sale marks, the earlier of which identifies it as having been sold at auction between 1814 and 1831. It is also thought to have been the microscope featured in an 1875 Harting exhibition catalogue and the example recorded in the collection of the Dutch zoologist R.T. Maitland (1823-1904).

Putting a value on such a rarity would have been difficult, but in the end the saleroom suggested £70,000-100,000. It sold on the day for £260,000.

By Ian McKay