Concave Rowland diffraction grating on speculum metal

Concave Rowland diffraction grating on speculum metal, grating area 49 x 34 mm, in wooden case marked 'V209.' Scratched markings on grating illegible. Manuscript note inside the case reads 'Ruled on Prof. Rowlands Engine Johns Hopkins University Baltimore Maryland U.S.A. 1898 Plate prepared at the Astronomical Physical instrument works of Mr J Brashear, Allegheny, Tennessee (sic) U.S.A. 1897 14438 lines to 1 inch 568 lines to 1 mm. Very bright one side. Definition excellent. V209'. This is repeated in German. A paper label on the box marked in German indicates (according to the donor) that the grating came from Paschen's laboratory.