I agree with CaptBones about his last merchants statements.
I have examples where merchants didn’t wear at all any flag, and U-Boot had to guess for their nationality.
Currently reading Peter Cremer biography, after sinking some cargos, he had to ask survivors in their lifeboats what nationality and ship name they sailed...
It even bring the terrible error when he sank a German ship coming back from china with a precious load!
I’m quite convinced some civilian ships in war time tried to hide their nationality until they crossed other boats they could trust.
But for an hidden U-Boot...
