Army trades were arranged in groups, A, B, C and D in a descending order of difficulty and time required in attaining proficiency. There are three degrees of skill, Classes III, II and I, in each Army trade which correspond with the grades of learner, journeyman and master craftsman where there is an equivalent trade in industry. The several rates of pay reflect the time required and difficulty in attaining proficiency in each class of each trade. Checker was a D Trade and he went from Class III in the trade to Class II. One thing I noticed, the documents you sent didn't have a record of his medals, that should be somewhere?
MaxD