Which was the world's fastest steam locomotive?

British railway fans will tell you it was the British A4 Pacific Mallard which reached 126 mph (203 km/h) on 3 July 1938, and since there is no claim for a steam locomotive to have gone any faster, that seems to end the discussion.

But there is the Deutsche Reichsbahn's 05 class, a 4-6-4 type, to consider, two of which were built by Borsig in 1935, and 05 002 reached 124.5 mph (200 km/h) on 11 May 1936. This UK webpage compares 05 002 with Mallard.

The 05 certainly achieved fame in Europe, regardless, and this book cover illustration seems to be based on one.