OK, this may be reaching here, but it is authentic. If you look down on your engine (towards the rear of the car in the center), you’ll see the hole in the fan-housing where the timing mark can be seen. Well, if you can see the timing marks, you don’t have this piece in place. It is a small rubber plug (311 129 000) that just pops in that hole (and keeps air from escaping).

Note from Everett: I found a reasonable substitute at my local hardware store - a "rubber stopper," size 5.5. A bit cheesy but for $0.68, it's a good substitute for something that is NLA.