The double-framed brass sextant was patented by Edward Troughton in London in 1788, and the form remained popular throughout the first half of the 19th century. This example belonged to Haverford College in Pennsylvania and may have been acquired when that school was founded in 1833. It has a silvered scale that is graduated every 10 minutes from -5o to +145o and read by vernier with tangent screw and swinging magnifier.
Ref: Edward Troughton, "Framing to be used in the construction of octants, sextants, and quadrants," British patent #1644.
