I see from the Book of Armies that during the Uther timer period there is an Elite Unit from Lindsey called the Black Marchers that have 9 points of magical armor but are not provided with any additional information about this peculiar unit of men. The question is this, does anyone know anything more about this unit and especially where they get their 9 points of additional "magic" protection from?

What page is this on?

What page is this on?

It is on Book of Armies, p. 12.

Thanks for the page reference
and No, no one knows anything more about this unit. It is just a piece of local color without any origin other than my imagination. The book, in fact most things I write, have such Easter eggs in them. They are for the gamemaster to use as he likes.
Consider them to be a mystery of the times.