This came from a local estate. The man worked at a Chrysler/ Dodge/ Plymouth dealership for many years. Unfortunately the family didn't know any details about it.
The main board is brushed aluminum over lightweight tin, and the letters are plastic with a mirror/chrome surface.
The "S" has some minor spots where the chrome has rubbed off (looks to have been touched up) and could use a light cleaning. Otherwise, it is in great condition.
Mounting hardware that came with it are attached with tape to the back.
Measures 23-1/2" long x 12" tall and the letters are about 1/4" tall off the board.