Astronomical Ring of an unusual type, signed "Butterfield Paris". Undated, circa 1690. This instrument is closer to an equinoctial ring dial than most astronomical rings.

Licence: Attribution 4.0 International (CC BY 4.0)

Credit: Astronomical Ring of an unusual type, signed "Butterfield Paris". Undated, circa 1690. This instrument is closer to an equinoctial ring dial than most astronomical rings. Wellcome Collection. Source: Wellcome Collection.