Concave Rowland diffraction grating on speculum metal, grating area 80 x 52 mm, with scratched markings reading 'Ruled on Rowland's machine / Johns Hopkins University Baltimore / 14438 lines to inch / to Capt. Abney / with kind regards / H. A. Rowland, Nov. 6 1882', almost certainly on a plate prepared in J. A. Brashear's works, with remnant of film used for cleaning grating on part of surface.