Also, the skyline casing, which was fitted at the top of the boiler, proved to be a trap for soot from the locomotive's exhaust. Consequently, these began to be removed from some examples of the class, leaving them with just the bullet nose.
The design flaw in the skyline casing, which was fitted at the top of the boiler, created a problem by allowing soot from the locomotive's exhaust to accumulate. As a result, some examples of this type began to have their skyline casings removed, leaving them with only the distinctive bullet nose.