The APLNext.ttf font with 325 glyphs does not explicitly include the 'EUR' glyph as well as certain other 'common' Unicode-based glyphs. The APLNext.ttf font was designed to be a file for use in .Net applications which is relatively small while still containing the 'APL' glyphs.
The 'EUR' glyph is displayed when the APLNext.ttf font is used in a .Net application because of 'Font Fallback' which is the mechanism used in .Net applications to render 'missing' glyphs in a selected front. UCS in VisualAPL is a cover function for calls to the .Net FontFamily class which incorporates 'Font Fallback', so UCS 8364 displays the Euro glyph. See here for more information: http://msdn.microsoft.com/en-us/library ... amily.aspx
The .Net 'Font Fallback' mechanism replaces the Microsoft-deprecated Win32 'Font Substitution' technology. The above MSDN link illustrates some control over 'Font Fallback' in a .Net application, but those procedures would not apply to a Win32 application, such as APL+Win.
Microsoft Word 2010 supports 'Font Fallback' and using Word 2010 it is possible to determine the 'fallback font' source for a 'missing' glyph. NotePad, WordPad and the Win32 RichText control do not, so the APLNext.ttf font may not be suitable in those simpler programs.