The way I understood it, the South African Contract diverted guns were in 4" only. These are the guns that were shipped from S&W to Capetown, but didn't arrive since they were diverted back to England. These guns don't have the arrow & U mark on the hump of the backstrap.

Here is one that I have along with its factory letter,














This is one of the Union of South Africa pre-Victory models that made it to South Africa evidenced by the acceptance marking on the top of the backstrap.