340PCS Starlock Washer. It is commonly used in our daily life and in industry. The starlock washer exerts a spring force between the fasteners head and the substrate to create more feiction and resistance to rotation.
Thanks Jeff I had wondered if it might be those
I took the other side off to look but there’s nothing holding the rollers on that side either other than the torsion bar end had been slightly peened over the rollers won’t come of that side,i can’t see that been the factory solution?