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Gunter's quadrant design is drawn on the face in colored inks and on the reverse is the declination diagram for mean years.
"B.W./AD 1770/calculated [for] the Meridian/o[f] Boston/July [11th?] 1770."
On the reverse "sic transit/Gloria Mundi."
Quadrants helped determine position on the earth's surface and were used in surveying for property and boundaries and for navigation at sea.