[Lynn Eades]

I would say strike marks Bob. They vary in their concentration but not in the way they are done.
David, British carriers used armour plate that looks like the smooth pattern you might see on sand that is levelled by gentle water action. A fine ripple pattern that was easily hidden by a coat of paint.
The Australians I believe developed their own bullet proof plate (BP2) As i recall production was held up for a while with welding it. I think stainless rods were at least the interim fix. I think the need for stainless rods was overcome during the Australian and New Zealand carrier production. Hopefully someone more in tune with Aust. pattern carriers can verify this.
My British built and welded hull AOP carrier (mid 41) was welded with stainless rods.
The un answered question I have is that some British built armour, (the heavy daimlier armoured car as an example) is made with the Canadian style "axe marked" armour plate. How did this come about? Was Canadian plate supplied to British industry?