Jumping back to plating. I want to create something that looks like the older rivet plating on a ship where the horizontal plates overlap. The vertical joints are butt joints. That brings up the question as to how thick were the plates?
The SHF John Oxley built in 1927 in Scotland : Here the plating was reduced in thickness where it was not needed to save money. The thickness ranged from 0.32 inch (8 mm) to 0.40 inch (10 mm). A discussion elsewhere talks about steam tugs from the early part of the 20th century with 3/8″ plating.
That gives a general range then. I’m not trying for exact .. just don’t want to get so extreme it would be venturing into the ‘silly’ Generally then .. 3/8″ to 1/2″ seems right .. that upper number from a 1885 issue of Marine Engineer.
In O scale 3/8″ = .008″ and 1/2″ = .010″. I have some .005″ brass which converts to plate about 1/4″ thick.