These are two of the information stands with comparissons between the states of the palace before and after the 2nd World War. The palace was occupied by the German army, just like Pavlovsk and Peterhof and several other palaces. All these palaces were totally destroyed, stripped to the bricks and beyond. All art and value that remained was looted. These two pictures show that.
The result is that all these palaces are in some way replica's. Build back to pre-war state with the help from drawings, photos, paintings, descriptions etc. Some of the paintings, furniture etc is original, because it was taken away before the Germans came. But all the interior art and architecture is a copy.
When you drive to the palace from Petersburg, passed Pulkovo airport and I believe near a railway crossing, you can see the original frontline of the siege of Leningrad.