Condensation marks inside front window

Hi I have a Bailey ranger 460/4 series 6 which I purchased last year,(our first caravan) what I thought to be marks on the outside of the front window turned out to be on the inside, it looks as if there has been condensation inside the window at some time which has dried out but still left some slight marks on one of the inside surfaces, has any one any ideas on how these marks could be removed. Other than this small problem completly over the moon with this van.