Metal "greeblies" of this model were added during the first movie and used in all R2-D2 units throughout the trilogy. Left and right legs belong to an R2-D2 used in Empire Strikes Back. One has the Empire paint scheme, while the other sports that of the Jedi.
A "complete" existing R2-D2 belonging to the studio will be almost identical to this piece, said auctioneers.
As an aside, remember the time when Narendra Modi ended his speech by saying "may the force be with you" in America, standing right beside Wolverine aka Hugh Jackman?
Well, he just outdid himself. After concluding his speech for the 68th Chartered Accountants Day celebrations, he exited the stage while Darth Vader's theme song The Imperial March was playing in the background.