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Individual objects described by auction houses, specialist dealers and collection catalogues. Attribution, dates and specifications remain source-reported unless independently established; rights clearance is pending.

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Tool · Ring & equinoctial sundial

Equinoctial Dial by Johann Christoph Keller

This equinoctial dial, held by the Museum of the History of Science in Oxford, is a silver portable instrument attributed to Johann Christoph Keller of Linz, dated circa 1580. Measuring 85 x 62 x 53 mm, the device features a rectangular base plate raised on four bun feet. The base is intricately engraved with floral and foliate motifs, alongside depictions of two angels positioned on either side of an inset compass. The compass includes magnetic deviation markings and cardinal points denoted as N, O, S, and W. Functionally, the dial utilizes an adjustable hour ring supported by two upright pillars, which can be calibrated to various latitudes. The mechanism includes a latitude scale marked from 0 to 90 degrees with a hanging plumb line for leveling. The instrument is signed by the maker on the hour ring, which displays common hours numbered from 1 to 12 twice.

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www.mhs.ox.ac.uk · 51108

Inclining dial signed by Johann Christoph Keller, featuring a brass plate on gimbals with a central compass and string gnomon.

Tool · Other sundial

Inclining Dial by Johann Christoph Keller

This inclining dial, held by the Museum of the History of Science, Oxford, is signed by Johann Christoph Keller and dates to approximately 1600. Manufactured in Linz, the instrument consists of a brass plate integrated into a wooden case. The brass dial is mounted on gimbals, allowing for adjustment to latitudes ranging between 45 and 55 degrees through the use of a sliding counterpoise positioned on the underside of the plate. A compass is set at the center, mounted on pivots to maintain a horizontal position regardless of the angle of the dial. Time is indicated by a string gnomon dial, with hours marked from IIII to XII to VIII, supported by a folding brass stand. The signature of the maker is inscribed at the top of the dial plate. The wooden case, which features brass round feet, is described as appearing to be modern.

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