Concave diffraction grating on speculum metal, grating area 53 x 38 mm, with scratched markings 'N.P.L. / BLYTHSWOOD RULING / RULED MAY 1926 / No. 53837', in velvet lined wooden case marked V379. German typescript label in case indicates that radius is 100 cm and grating has 14402 lines per inch. A paper label marked in German indicates (according to the donor) that the grating came from Paschen's laboratory.