bkev wrote: Okay, perhaps I'm being cynical but - with the recent revelation that the LoC doesn't even have a copy,

The LoC has multiple copies (Copyright Deposits) of each film. They are prints which were provided after each of the initial movie runs in theaters. They are used and worn.

Here is the Copyright Deposit information for Star Wars (1977): http://lccn.loc.gov/96512247

The recent revelation (not so new actually) is that the National Film Registry (a subsection of the Library of Congress) did not receive the new copies they asked for. The NFR was created so that when the public voted a work as significant, the NFR would ask the original creator for a new clean print to be struck and submitted for preservation.