[1] When design work commenced after the signing of the contract, however, it was discovered that the other tendering firms had been correct and that the locomotives could not be built within the specified weight limit, if the specifications were to be adhered to.

It was eventually agreed that Krupp should design a suitable smaller boiler which would bring the locomotive's weight down to a level which would be in line with the stipulated maximum.

Even with the smaller Krupp-designed boiler, the locomotive's eventual working order weight was still more than 2 long tons (2.0 tonnes) over the desired maximum.

As was done with the tenders of the Classes S and S1, the top sides of the coal bunker were scalloped out to improve the crew's rearward field of vision.

They also relieved larger locomotives like Class 3R and others from shunting to be dedicated to pickup work and hauler service between the harbour and the Bellville yard.

Their number in Cape Town rose to more than thirty by the mid-1970s, when eleven engines would handle the dock shunting on a daily basis and six or seven could often be seen coupled together going to and from Paarden Eiland shed at shift changes.

[4] In 1972, two new Blue Train sets built by Union Carriage & Wagon in Nigel entered service and were stabled at Capital Park in Pretoria.

The outline of a traditional SAR locomotive number plate was used as a commemorative cancellation for De Aar on the date of issue.