I know this isn't an actual prop but as a piece of production material from the editing process it is an important piece of film history which I hope will be of interest here.
I bought it recently on ebay in the UK and got it this morning. I knew it was pretty rusty so it wasn't a nasty surprise to see its condition.
I had the afternoon off and set to cleaning the tin to remove the rust and get it to a state where I could safely open it. Needless to say, it took me hours to do properly and when the lid finally came off the inside of each tin half had rusted to the point of covering the tape reel both sides. I gave it a careful brush over and continued to get rid of all the rust on the tins. There is a loose paper label with the reel and a detailed list on the inside of the lid, the reel is also marked.
I don't have a clue as to the content other than what is noted. I don't have the means to play it either and am mainly happy to have it in my collection as my most vintage piece. For more info here is the auction page:
ALIEN REEL FROM 1979 on eBay (end time 29-Aug-10 23:00:47 BST)