late 70s or early 80s ... Is there any likelihood that the whisky is still good? Does it have any other value in the marketplace?
Just like wines that have been found in the holds of sunken ships from a century or more ago--it might be spectacular. There is always the possibility that seal is loose, or the cork decrepit, but I would give you $42 for it any day of the week, and if I did, I probably could be criminally prosecuted for theft? fraud?
Chances are that bottle is one sublime little jewel.