This roof cover came with the car. I can't really see the point of it. It is however made especially for the 124 and carries the Pininfarina logo. The elastic straps hook over a chrome eyelet which attaches to the end of the chrome strips to keep it all nice and taught. (I couldn't be bothered to fit the eyelets for the pic). So, is this a rarity? Or were all spiders supplied with them?
Never seen one. It's a good item for keeping the sun from tearing up the interior and the top. Seems it would have been better designed to cover the whole windshield, and have flaps to cover the side windows. I'm thinking that you have an aftermarket item.