I think this leaves only one character in the old Symbol font that does not have a Unicode equivalent:
RADICAL EXTENDER (decimal 96 in the Windows version)
Or does anyone know where it can be found in Unicode?
Not in Unicode.
Postscript radicalex is an odd character, imaged as a space followed by an overline to the right of the current position so that the next character entered appears under that line but preceded by the space.
In plain text it did not work for its supposed purpose because of that extra spacing. A simple non-spacing digit-width overline without the leading space would seem to be what should have been provided.
I would guess it was used on occasion by equation building software which would overlap the initial space part of the character.
But under Unicode plain text U+0305 COMBINING OVERLINE would seem more useful.
One might propose a new character RADICAL EXTENDER OVERLINE which would be a combining overline guaranteed to be at exactly the proper height to join the radical.
The only reason I can see for encoding Postscript radicalex in Unicode would be for compatibility purposes if it has in fact been used with a large body of data.
I suppose if one were translating to Unicode and came across this radicalex followed by a character X one could replace it by U+00A0 NON-BREAKING SPACE followed by X followed by U+0305 COMBINING OVERLINE.
Jim Allan