On May 17, Cologne auction house Lempertz is selling 115 bronze mortars from the 8th-18th centuries including this 85kg bronze example dated 1609 which is expected to bring €30,000.

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They form a tiny part of what is considered to be the world’s most extensive collection of mortars, amassed by Ernst Genz (1911-91) and his son over many decades. It is known as the Schwarzach Collection after the small south-west German town where it is housed.

Among the many impressive pieces up for sale is this 11in (28cm) high cloister mortar from Le Puy-en-Velay, an important religious centre near the Loire River and starting point for French pilgrims en route to Santiago de Compostela.

The bronze mortar is dated 1609 and is no lightweight: it hits the scales at 85kg and is expected to bring €30,000.