My brother, Blaine, who is technical director of this blog, has again earned his salary which is R0 per month. In providing the answer, he has stretched the original picture to compact the gables in order to make them look more like the postcard. He contends that there are 3 significant features that correspond. There are also the 3 skylights and ventilators per roof. Perhaps it was originally a store needing no windows and later a factory and they added windows in front and back (see last pic)
Main picture: This is the photo which initially created the commotion
What did Mosenthals produce here and was this company known as Valley Textiles as some allege?
Assistance in identifying this building was provided by Blaine McCleland, Ralph West and Garth Sampson