4ksq tail light lens

[Dave Fain <KC3565L@sprintmail.com>]

Just noticed that my '85 4000S Quattro has a left tail light
lens that doesn't match the rest of the lenses.  It looks the
same from a distance but has a horizontal groove about 1/2"
deep between the red and amber parts.  Other than that, it
fits perfectly.  Anybody know what sort of Audi this belongs
on?  Is this a rare and hard to find part that somebody would
like to trade me a correct lens for?  Probably nobody but me
will notice it, but now it annoys the H*** out of me.
Dave