>I think the .notdef glyph in the conext of the Last Resort font serves a >slightly different purpose, since it is not indicating only an absent glyph >but an undefined character code.
That's true, it makes no distinction. The context is a system that normally searches all available fonts for a glyph at the given codepoint. If you see the .notdef glyph it is telling you that "no font installed on your system has a glyph for this codepoint." There are also different glyphs that appear for the PUA codepoints, for illegal codepoints, and in a few other cases.
