I found this book in an antique store today. 1951. Some chapters are: change over, boilers, boiler construction, pumps, forced draft blowers, fuel oil systems, boiler feed water, steam plant operation, fireroom operations, boiler maintenance & repair, casualties and their handling, compressed air systems, oil and water king, distilling plants, records & reports, shipboard damage control, and more. There guys must have been tough old salty dogs...and they earned their pay apparently from reading just a bit into this 'restricted' book...
Working on steam and hot-water systems isn't rocket science....it's actually much harder.