I had occasion to visit the dam in the late 60’s on a canoing expedition. The much lighter tone of the replaced semi-circular section was then very apparent and can just still be discerned on the colour photography posted.

The building behind the dam on the RHS lake edge as you look at it is (or was) a pub restaurant; from which we little ambassadors of the “U.K. forces of occupation ” duly competed in skipping stones across the lake towards the Dam.