Checked on this and unfortunately no other details on the steel cartridges in the book.

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Fastest construction of a sea-going merchant vessel was Libertyship Robert G Peary : four days and 15 1/2 hours from keel laying to launch and was completed ( fitted out ) just three days later.

http://ahoy.tk-jk.net/macslog/WW2Lib...TheBridge.html

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