Neil,
I guess it must be a typo; "Steam Locomotives Of The South African Railroads" by D.F Holland regarded as the definitive work on SAR locomotives, shows the 19D as the last of the 19 series.
Ennech,
Your 15F is coming on very nicely,, do you plan on selling drawings and castings?
When I finish my current loco, which is also my first, a 5" gauge Railmotor, and probably still a few years to completion, I am hoping to build a SAR engine.
Clive