Optical Gratings, 100/300/600 lines/mm

Set of three original Paton Hawksley gratings with 100, 300 and 600 lines/mm, mounted between plane-parallel glass plates in a 90 × 30 mm card frame. Each grating has an area of 9 × 16 mm; the 300 lines/mm grating has an actual density of 295.28 lines/mm.