Sears introduced the "Commercial" badge around 1974 with no changes to the actual lathes. The primary differences between the early 12" Craftsman and the late 12" Atlas and Craftsman are that the late ones have 1/2" thick ways instead of 3/8" found on the early ones and all 9" and 10". In addition, the late 12" have heavier headstock, tailstock, carriage, cross slide and compound slide. And the back gears are in the headstock below the spindle instead or attached to the rear of the headstock. The gears, however, are the same.
In addition, the final 12" version introduced in 1967 has a slip clutch on the lead screw, a lever to engage power cross feed, and a heavier right lead screw bearing with ball thrust washers.
The only differences between the cabinet and the bench/stand versions of the two late versions after 1957 are in the belt drive mechanisms (spindle pulleys and countershafts).