259. An injury is graded as follows:
(a) Injury Grade (1) – permanent loss of an eye or any part of the body on account of special occupational hazard or injuries even more serious than such loss;
(b) Injury Grade (2) – an injury on account of occupational hazard leading to a more serious injury;
(c) Injury Grade (3) – an injury on account of occupational hazard resulting in a serious disability which the person may permanently suffer from.