This come in a Job lot ,I know it’s not from a MK2 ,but someone may have come across it
That is a slider, from an NDV window: common on many British sedans. I’ll take a pic of one on my Rover, later on.
I cannot say if for sure it’s a Jag part, but it certainly looks the same as ones I recall.
On the rear NDVs, of my Rover.