Early Vendo 39's with the tall condensor should have this cover.  It helps push the hot air from the compressor away from the bottom of your machine.  It also helps keep the machine from being too close to the wall.  Many of these were made of cardboard and were crushed.  The later ones were made of steel and were painted to match the machine.  This steel piece will need to be painted to match your machine. 

Overall dimensions approximately: 18.75 x 14.25 x 3

Picture shows it next to an original cover.