What is this part?

Can you identify this panel?

I got this in a box of parts with a Dart I recently picked up. Is it a dash filler? Like if you don't want to use the factory speedometer? Or is it a body patch panel?
The part is aluminum. It is marked "Dart" and what looks like "AMD"
Also, if you know what it IS,,what does it cost new retail?
Thanks in advance!
Greg Purcell