Buick fender skirt question

Hello,

While driving through Chicago the other day I saw what appeared to be an early 90's lesabre with fender skirts on it. Ive never seen fender skirts on such a late model buick, but since olds had the permenate skirt installed on some models I thought maybe it was some super rare feature. Whats the deal with these, are they stock? It wasnt a show car, so I doubt it was something he had made custom for the car.

I was wondering if aftermarket fender skirts can be applied to a 92 park avenue?

Thanks,
Josh