Originally posted by Don Cardi:
There are several reasons that a studio would use a stand in back then. The most common reason would be for a situation like this one; The scene at Woltz's place may have already been shot and now Duvall is over shooting another scene at a totally different location.
In this case, it was basically just the fact that the stars were shooting in NY, and the estate was in Cally, so they used a second unit to shoot these scenes....