Revolving Bell Engine by Daniel Davis, c. 1848

Daniel Davis (1813-1887), Boston. Electromagnetic motor, consisting of a vertical steel U-magnet, a revolving iron bar between the poles with electromagnet and a gear with bobbin counting the revolutions on a bell on the top, on circular walnut base, overall height 12 ½ in., missing the rotor commutator and one brass blade. - Note: Daniel Davis was a self-educated engineer with a keen interest in electrical instruments. In 1835 he set up in business for himself and began to manufacture and construct instruments to illustrate the general principles of voltaic and dynamic electricity. In 1842 his book on magnetism entitled "A Manual of Magnetism" with accompanying catalog was published, a standard work for colleges and high schools with many practical demonstrations.

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)