I don't think I've ever seen then with a white thing over the height adjuster rod before.Must be a rare piece.
What is it? A hose fitting?
At first I thought someone had fitted a washing port to attach your hose for cleaning the underside, as some expensive mowers feature, then wondered how it would work with the fitting facing the rear instead of downward.
It looks like a previous owner has just jammed an old hose nozzle under there to dampen a rattle.
