This is a square Porsche Martini racing sign.  We upgraded the lighting to LED in this sign, and it really looks great, both night and day. 
 
When it is not illuminated it is a dark blue, and when it is illuminated it is the lighter blue color you see.  It looks great both ways.  
 
Not sure of the age of it, but it does appear older.  It has some typical surface scratches and the can has some minor discoloration since it's white.  
 
Measurements: 
24.5 inches square
4.75 inches deep