These are called skeuomorphs.
From Wikipedia's article on skeuomorphs:
A skeuomorph is a derivative object that retains ornamental design cues from structures that were necessary in the original.1 Examples include pottery embellished with imitation rivets reminiscent of similar pots made of metal.
A similar alternative definition of skeuomorph is "a physical ornament or design on an object made to resemble another material or technique". This definition is broader in scope, as it can be applied to design elements that still serve the same function as they did in a previous design.
Skeuomorphs are deliberately employed to make the new look comfortably old and familiar.
In movie and film specifically, they are often called period objects or artifacts.