pilkie said:Hi Richard.
Take a look at all of your glass panels! some may have been replaced over the years and may be plain!
I dont think it wears out with age!
I suspect that the various makers,rover,ford,triumph,bently,rolls etc had it made to different specs,and tint colours,so some appear darker than others.
My old 1971 XJ6 had syndym,and I remember it was a bit darker than the rover.
Dave