Thanks for responding - but, having tested, that is not the solution.
I was (am?) under the impression that the Document Type Declaration <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML .01//EN" "http://www.w3.org/TR/html4/loose.dtd"> superseded the header Content-type: text/html.
No ? Note, I generally use the "Strict DTD" but left in "loose" in this test in order to rule out that possibility.