The movie industry experimented 
                  with the concept of double siding as far back as the 1950s on 
                  a few major films. Several major films, i.e. Breakfast at Tiffany's 
                  in 1961 and Zulu 
                  in 1964 released a double sided version. 
                As National 
                  Screen Service relenquished their control of paper distribution 
                  back to the studios, and the studios started eliminating sizes 
                  and restructuring paper distribution, the concept of double 
                  siding arose again. 
                In the mid-1980's, the 
                  studios reduced the distribution overhead by eliminating window 
                  cards, inserts, half 
                  sheets and drastically cut back on larger paper. 
                At the same time, the studios 
                  started producing more expensive double-sided posters that gave 
                  a more realistic look. 
                Studios produced both single-sided 
                  and double-sided printing. The single-sided posters have printing 
                  only on the front side with a white backside, while double-sided 
                  posters have the same artwork on the front and backside. The 
                  artwork on the back is reversed (in lighter shading). Double-sided 
                  posters are normally printed on a thicker paper than are the 
                  single-sided version. These posters are displayed in "light 
                  boxes". Because of the reverse artwork on the back, the 
                  double-sided printing gives a more life-like look to the poster 
                  when a light is placed behind it.
                The doubled-sided poster 
                  is the result of a very expensive printing process which involves 
                  running the initial negative through at normal color intensity. 
                  The poster is then reversed and run back through the presses 
                  at a reduced color indensity, such as 30% to 40% of the initial 
                  color. This is why the artwork on the front is more colorful 
                  and detailed than the reverse print on the back.
    For example, here is the reverse side 
      of the one sheet for the film The Grinch:
    
    Doubled-sided posters are extremely 
      popular with many collectors of newer materials. In fact, because of the 
      increase in good quality reprints,some collectors will ONLY collect one 
      sheets that are double-sided, if available, and will pass on their single-sided 
      counterparts. 
    Some video 
      posters are referred to as double-sided. Normally in this case, the backside 
      of the poster is not just a lighter version of the front side's artwork. 
      Double-sided video posters have different artwork on each side. The poster 
      may contain two different versions of the artwork for the same movie, or, 
      in some cases, the artwork is from two different movies.