Install the patch providing Euro currency support on Solaris 2.6 - see:
/net/sunsoftpatch/patches/temporary/T106842-01
If you don't have them yet, this also requires the following patches:
/net/sunsoftpatch/patches/temporary/T106841-01
/net/sunsoftpatch.eng/patches/patchdb/unbundled/openwin/3.6/105633-11

Reboot your machine, choose the de.ISO8859-15 locale from the login screen.

Run the application test/java/awt/im/IMFTest, using the command line option -Dfile.encoding=ISO8859_15_FDIS to work around bug 4171977.

Click into the field that's labeled "Lightweight component, non-client" so typing goes into this component. Type AltGraph-E. You'll see the Currency character (\u00a4, a circle with four spikes). You should see the Euro character.