the axle load of of these tenders exceeded the permissible limits on the branch lines for which the Class 19D was intended. Upon delivery, their new Type MT tenders were exchanged for the smaller modified Type MP1 tenders from some of the reboilered mainline locomotives. The Type MP1, many of which were later rebuilt to Type MR tenders, had a lighter axle load of and was therefore more suitable for branch line work. This policy was followed with all the Classes 19B, 19C and 19D, except the last batch of Class 19D for the SAR, numbers 3321 to 3370. During 1944 Dr. M.M. Loubser, then CME, who had been involved with the design of the Class 19 family from the very beginning in the late 1920s, made further improvements to the Class 19D. All the post-war locomotives came equipped with vacuum brake systems in addition to the steam brakes. The two vacuum cylinders were fitted under the running boards on either side at a point about midway between the leading and driving coupled wheels, while the vacuum chamber was arranged in line with the intermediate coupled wheels. The final batch from NBL, numbers 3321 to 3370, had Type MX tank wagon type tenders with cylindrical water tanks, similar in appearance to the American Vanderbilt type tenders. They were built to the design of Dr. M.M. Loubser, ran on three-axle Buckeye bogies and became commonly known as Torpedo tenders. Service South African Railways During the service life of the Class 19D, several tender exchanges occurred to best equip a locomotive for the region it was allocated to and the type of service it was to be employed in. In line service, type MX Torpedo tenders were usually preferred for their larger coal and water capacities. The result was that by the time the Class 19D was withdrawn from service in the late 1980s, many had exchanged their Type MP1 or Type MR tenders for Type MX Torpedo tenders and vice versa. Type MX Torpedo tenders also ended up attached to Class 19B and Class 19C locomotives. The Class 19D was the most numerous South African branch line locomotive and, at 235 built for the SAR, was only twenty less in number than the Class 15F mainline locomotive, the most numerous South African steam class. The Class 19D was very versatile and saw main- and branch line service all over South Africa