The Class 6E1 was produced in eleven series over a period of nearly sixteen years.
While some Class 6E1 series are visually indistinguishable from their predecessors or successors, some externally visible changes did occur over the years.

The Series 6 and Series 7 locomotives are visually indistinguishable from each other, but can be distinguished from all the older series models by the rainwater beading that had been added above the small grilles on the sides aft of the side doors.
Beginning with Series 8, all subsequent series had a large hatch door on each side to the right of their side doors.
The Class 6E1 was produced in eleven series over a period of nearly sixteen years. While some Class 6E1 series are visually indistinguishable from their predecessors or successors, some externally visible changes did occur over the years.
The Series 6 and Series 7 locomotives are visually indistinguishable from each other, but can be distinguished from all the older series models by the rainwater beading that had been added above the small grilles on the sides aft of the side doors. Beginning with Series 8, all subsequent series had a large hatch door on each side to the right of their side doors.
South African Class 6E1, Series 7