Thanks to Overun
for posting the image on my behalf,
lomapaseo, thank you for your comment as well, these are things I am not properly aquainted with hence I asked the question.
Point taken with regard to the discoloured area itself, what intrigued me was the orderly pattern of what I perhaps mistakenly refer to as a witness mark, to me it appears that something was there to create such a well ordered pattern, that's why I asked if that "shape" is something that somebody recognises as being the outline of a component, and if so what ?
It could well be that is comes from nothing more than an object that the part ran into on it's way out of the conflagration, or, it may be pertinant to the sequence of events, that isn't for me to comment on .. apart from ... any ideas what we might be looking at here ?
TR