OK history & Convertible experts. Here is a spoiler I've never seen before. Anyone have information on this?

Rare Lon? No, but the car is.

Thats the spoiler used on the 87-90 Firebird/Formula/TA/GTA verts by ASC. Its only as rare as the car itself.

Oh BTW, I've seen them before. First one I saw was at a dealer in 1989.

Your links didn't work...

copied and pasted and they work...
If there is any doubt, Madmax is right.
ASC Firebird convertibles converted before 91 all use this spoiler.
Not sure about the base 91-92 Firebird convertibles, haven't seen a picture of the back end.