A million-dollar look from an old poster:
That is the Sir Winston Dugan*. Numbered 620 (and first of its class - class 620), it had a chrome grate over the smokebox to "emulate" the grills on automobiles of the time (and was the only loco given this treatment). It was dark green with yellow stripes.
The poster comes from the Boston Public Library. Here it is, full-frame:
Sure, the SAR's 140-ton "flagship" was streamlined to commemorate the South Australia Centennial celebrated in 1936. Unfortunately, it was scrapped after the 620's replacement by diesel-propelled railcars in 1950s. Some photographs:
(All photos by sarail 2009 @ Flickr)
And one more photograph (by railfan3) showing the 621 together with probably the world's most famous steam locomotive, the Flying Scotsman during the latter's visit to Australia in late 1980s:
* Sir Winston Dugan was a British WWI war hero who rose to the rank of Major-General in the 1930s. He was appointed Governor of South Australia in 1934. He went on the become the Governor of Victoria in 1939. He retired and returned to England just after WWII.
Source: The Railroad Forum