Copper firebox

Copper through the ages, Copper Development Association, 13th printing, 1956

 This locomotive, the William Shakespeare, was featured in a book published by the (British) Copper Development Association as an example of modern use of copper in transport. The firebox, 10ft long, 7 ft 1 inch wide and 7 ft high was made of 5/8 inch copper sheet, with the crown sheet 1" thick. Presumably calculations determined that the crown sheet would withstand the boiler pressure of 250 lbs per inch, but...