tenorized treble clef

[Janek Warchoł]

Hi,

LilyPond has a treble clef with added C-clef-like stuff:

{ \clef "tenorG" c' }

(http://lists.gnu.org/archive/html/lilypond-user/2013-11/msg00661.html)
However, it seems to me that these added lines should be positioned
half a staff-space lower.  After all, C clef indicates the position of
middle C:

{ \clef "tenor" c' }

The way we have it right now, the extra "claws" point to d instead of
c.  I see that the engraved example provided in the thread linked
above has this positioning, but I think that's a mistake on the
clef-punch manufacturer's side.  What do you think?  Does anyone have
more examples of such clef?

best,
Janek