1.1 This standard contains the principal physical characteristics and metrological requirements for weights which are used - for the verification of weighing instruments; - for the verification of weights of a lower class of accuracy; - with weighing instruments. The nominal values of mass of the weights covered by this standard range from 1 milligram (mg) to 50 kilograms (kg). 1.2 This standard applies to weights in classes of accuracy as follows: E1, E2, F1, F2, M1, M2, M3. 1.2.1 Weights used for the verification of weighing instruments The classes of accuracy of the weights used for the verification of weighing instruments shall be specified in the appropriate International Recommendations relating to these instruments. 1.2.2 Weights used for the verification of weights of a lower class of accuracy E1 - Weights intended to ensure traceability (see GSO 1651/2002 paragraph A.3) between national mass standards (with values derived from the International Prototype of the kilogram) and weights of class E2 and lower. Class E1 weights or sets of weights shall always be accompanied by a calibration certificate (see 12.2). E2 - Weights intended to be used for the initial verification of weights of class F1. Class E2 weights or sets of weights shall always be accompanied by a calibration certificate; they may be used as class E1 weights if they comply with the requirements for surface roughness and magnetic susceptibility of class E1 weights and if their calibration certificate gives the appropriate data (specified in 12.2). F1 - Weights intended to be used for the initial verification of weights of class F2. F2 - Weights intended to be used for the initial verification of weights of class M1 and possible M2. _________________________ (1) E: Exceptional, F: Fine, M: Medium. M1 - Weights intended to be used for the initial verification of weights of class M2. M2 - Weights intended to be used for the initial verification of weights of class M3. 1.2.3 Minimum accuracy class of weights used with weighing instruments The accuracy classes of weights used with weighing instruments shall be chosen in accordance with the requirements of GSO 1698 / 2005 “Nonautomatic weighing instruments”. F1, E2 - Weights intended to be used with weighing instruments of accuracy of class I. F2 - Weights intended to be used for important commercial transactions (e.g. gold and precious stones) on weighing instruments of accuracy class II. M1 - Weights intended to be used with weighing instruments of accuracy class II. M2 - Weights intended to be used in normal commercial transactions and on weighing instruments of accuracy class III. M3 - Weights intended to be used on weighing instruments of accuracy classes III and IIII.