It is the window stop. I just put new ones in my '96 F to sort out the windows which were always pushing up into the hood and the rubber seals around the windscreen. The 2 I found in the bottom of the doors were white which were the original parts yours looks like a picture of an update I saw. New updated replacements can be sourced from several places on the internet - can't remember where mine came from, Possibly MGspares on ebay as I have had a few bits from them.
Roger