Yes Eric it does look exactly like the gun James Mason is holding because it is the actual gun used in the film, here is part of the post I had put on another forum some time ago.
In 1984 a friend of mine who worked in the Birmingham Gun trade contacted me and asked would I be prepared to lend a customer of his my Purdey shotgun. It turned out that his customer was a property master working in the British film industry and was searching for a usable antique Purdey shotgun, it had to be the type of gun an elderly member of the aristocracy would have owned around the 1900s and my gun was exactly what he was looking for. After extracting the usual assurances that if there were any damage no matter how slight to the gun my friends life would become forfeit and his children and wife would be sold into slavery and any profits from the sale would of course be mine, not to harsh a deal I thought for what they were about to have on an extended loan. In reality to find a usable Purdey Bar in wood thumb lever shotgun built in 1860s, complete with its original unsleeved Damascus barrels Nitro Proof is rather a rare gun to come across yet alone borrow for the duration of a film. The gun was used in two scenes of the film firstly Sir Randolph Nettleby (James Mason) is holding it talking to Cornelius Cardew (John Gielgud) after Cardew had walked in front of the gun line with a placard, lastly in the scene after Tom Harker (Gordon Jackson) is shot Sir Randolph Nettleby’s loader is supporting it on his shoulder. The gun was not actually fired in the film because the Insurance company where not to keen for the actors to use a hundred plus year old gun, it being the oldest gun on the set even though they were assured the gun was perfectly safe to use with black powder stage blanks by the Birmingham Proof house, probably the disaster that occurred on the first attempt to start filming was still very fresh in their minds. The financial reward I received for my help in solving his problem was not a large sum but enough to have some cosmetic work done on the gun.
At the time I had no idea what film the gun was to be used in but as the saying goes if only I did know then what I know now I would have asked for a film poster signed by all the actors. I do find the final scene of the film extremely haunting because it does not need much imagination to know what is approaching to take the lives of the young men in the film as we the audience are looking at it with full knowledge of the First World War to come. And just a personal note I have always believed that the decline of the English bespoke gun industry was caused in no small way by the untimely deaths of thousands upon thousands of sons on all sides from the upper middle and working classes, caused by the War “no customers after the war and no sons to continue to purchase later on” and of course the same fate was to become the artisans and craftsmen which accelerated the industries demise to the now shadow of its former self. The film is of a deliberate slow pace and extremely well-acted though to be able to understand the English class system which I personally do find unacceptable and very difficult to rationalise as to why so few people should be so privileged and own so much, but there is always a but isn’t there, without it we would not have some of the most beautifully designed and mechanically refined sporting guns the world has seen, built by such names as Holland & Holland, Purdey, Boss, Churchill, Grant, Lancaster, Lang, the list could go on and on. Though the picture of a driven shoot painted in the film of guns at their pegs having loaders passing a reloaded gun to increase the overall take speed all surrounded by the swirl of black powder smoke and falling pheasants you can call it slaughter if you like, though Sir Randolph Nettleby does have a few words to say on that subject in the film. A copy of the film is as close as it gets to us looking through that window in time at a picture of British Edwardian aristocratic shooting history.
but the failure analysis, metallurgical study, composition analysis, tensile testing, MPI and radiography came to about $2500. I told my wife that we'd make a little money if I could get everything published 
