Hej Holger!

 HG> However, if diaeresis is the same as the 'divide' sign

It is the 'o' character with two dots on top.  The 'o' character with the
'divide' sign - I call it the slashed 'o' which hardcore encoding gurus call
'LATIN SMALL LETTER O WITH STROKE' - is decimal 248 in latin1 and doesn't exist
 in CP437.

 HG> In Latin 1 it's represented by chr code D8

That is 'LATIN CAPITAL LETTER O WITH STROKE' and also doesn't exist in CP437.

 HG> In Latin 1 it's represented by chr code D8 or dec.216 which
 HG> happens to be the same as in CP 437.

No it isn't.  According to https://en.wikipedia.org/wiki/Code_page_437 D8 or
dec.216 is a line drawing character and in latin1 it is 'LATIN CAPITAL LETTER O
 WITH STROKE' or character '├ÿ' in utf8.

 HG> "IBM OS/2 Warp 4" "Keyboards and Code Pages"

I found a pdf online entitled "OS/2 Warp Server for e-business, Keyboards and
Codepages" and do not see PC8 listed in there.  It does have 'Codepage 437' and
 'Codepage 819 - ISO 8859-1' and comparing them shows the same results I have
stated above.

 HG> MK> '...' En Møøse hade en gång min syster ...
 HG> What is this .................^^ in Latin 1?

F8 or dec.248 (not a character in CP437) for the second and third characters in
 M├╕├╕se, and E5 or dec.229 (86 or dec.134 in CP437) for the second character
in gång.  The encoding gurus call it "LATIN SMALL LETTER A WITH RING ABOVE"
which I believe in Swedish is called the small letter angstrom.  Please correct
 me if I am wrong.

Livet är gott,
Maurice

... En Møøse hade en gång min syster ...
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 * Origin: Little Mikey's EuroPoint - Ladysmith BC, Canada (2:280/464.113)