71 duster decklid wing

Sharing pictures of it would be a good start?

Members here would be able to tell you pretty quickly if it’s an aftermarket one if you post several pictures of it (top and bottom of trunk lid).

But if you can’t post pictures, of the leading edge of the wing has a sloped angle of 18 degrees, instead of the factory 19.2 degrees and the nut on the underside, left most to the drivers side quarter panel is a stainless steel colour instead of nickel plated colour, then it’s NOT a factory wing. Be sure to post up the chord measurement too as that’s a key detail. But if the width of the wing is 48 7/16” then it MIGHT be a factory wing. Some of the aftermarket wings were 48 9/16” wide so that’s something else to verify.