Square replica reflection grating (52 x 52mm) on glass substrate (he 25 x 60 x 60mm)

Square replica reflection grating (52 x 52mm) on glass substrate (he 25 x 60 x 60mm), 150 lines per mm, 5000 Angstrom blaze wavelength and 2º 09' blaze angle. Made by Bausch & Lomb, Rochester, New York State, USA in 1984, Cat. No. 35-53-06-201, Serial No. 1055-33-2-2. Supplied to the University Observatory, Oxford through Glen Creston, 16 Dalston Gardens, London. Separate note indicates the grating was used with a spectroscope at the La Palma Observatory in the Canary Isles.