Early 3.1/162 mm (Approx.) Portrait Lens, c. 1860

France. Unusual double achromat lens composed of two closely-spaced achromats (with 15.6 mm air gap to avoid vignetting) of the same focal length and 53 mm diameter, both marked "B.F.90" and an abbreviation on the rim, ht. of optical tube 31.1 mm, elements with a few cement imperfections. – Note: The optical tube can only be inserted into an intermediate tube from the back (since only the front part is blackened inside the tube), which in turn can only be inserted from the front into another intermediate tube (with a maximum extension of approx. 30 m) which is then screwed into a focusing mount with focusing (extension 15 mm possible) from the front. The total height is 11.2 cm, with a 23 mm aperture (f/7) that can only be screwed on from the front. – A sophisticated lens from the early days of experimental lens construction.

布雷克拍品等级是为了方便竞买人判断拍卖品的成色而设置的。布雷克等级用1到6级来标注外观和功能的成色，(从非常好到非常差)。 在目录图册里用括号里的2个数字来表示，前一个数字表示外观成色的级别，后一个数字表示功能成色的级别。如(3/2)表示外观成色是3(满意的)，功能成色2(好)。 成色 定义参照下列标准： 1 - 非常好 (未使用过，没有使用痕迹) 2 - 好 (新，极少的使用痕迹) 3 - 满意的 (普通的使用痕迹) 4 - 及格的 (明显的使用痕迹，某个非主要部件是后配的) 5 - 有缺陷的 (极明显的使用痕迹, 某个主要部件是后配的，功能上有缺陷，需要修理) 6 - 非常差 (严重破损, 缺少重要部件)