Hermagis brass lens. Aplanetic lens N°4. Focal length 400mm, F/7. C. 1870 Hermagis brass lens. Aplanetic lens N°4. Focal length 400mm, F/7. C. 1870. With mounting ring. Covers 18 x 24 cm. Height 13 cm. Diameter 4.7 cm. Some slight scratches on the rear lens without impact on use.