object in radiator

I popped the cap off the radiator in my newly purchased 97 bonneville, and found a metal ring around the inside of the neck to which was attached a woven metal strap and a short metal rod with a rubber bumper on each end. There was something else attached to this thing which fell off into the radiator when I tried to remove whatever that thing is. What the hell is this thing and is it OEM or aftermarket?:confused:

Thanks

It sounds like some aftermarket gizmo intended to reduce corrosion buildup in the radiator.