Abdul666 asked a question about the origin of the tank depicted on the cover of Voices Prophesying War, there are elements of five illustrations on the cover of the book and all of them are also inside the book with annotations of some sort showing the origin except the tank. Abdul666 was quite correct that the airship was taken from one of the works of Robida.
Looking through The Tale of the Next Great War I found this illustration
Although there appears to be no comment in the text of The Tale of the Next Great War it has this annotaion underneath the illustration.
'The first patent application (No. 747) for an armoured fighting vehicle was presented on 3 April 1855 by James Cowen and James Sweetlong.'This invention consists of an improved locomotive battery to be used in the field of battle, and is so constructed as to exert a most destructive force against the enemy , while protected from damage in return' '
This has piqued my interest, Im not sure the illustrations are directly linked to the patent application or not, google has so far not come up with any answers.Im going to see if I can find out more information.