I have to say that maroon 3f does have flanged middle drivers so I think somone has been modifying it, 3F was introduced in 58, in 65 was factory weathered, probably a first by a manufacturer, and 66 in midland livery, lasted until at least 1968 so not a bad run for a model.
Even more interesting, apparently it was released as 43620 in BR maroon with late crest in 66/7 but never seen one like that.