[Warning: Spoiler alert, if you haven't seen the movie.] Do a YouTube search for "making of twelve angry men" and you'll see dozens of analyses, discussions, comments by the actors, and more. This film, while not a commercial success domestically, did well internationally. It's been remade at least twice here and once in Russia! Several TV shows have incorporated the general story line as an episode or portion of an episode. Hardly a year passes without some amateur stage production of the story somewhere in America! The movie is used in film schools and even high school civics classes, and it's been recognized by the ABA as a sterling example of the legal system at work (even though Fonda's character and the others engaged in illegal activities!) It is practically a course in directing and cinematography, and its somewhere on virtually every "best movies of all time" list--AFI, IMDB for two. The story by Reginald Rose was originally done as a live TV drama in 1954. Henry Fonda liked it so much that he decided to produce it as a movie.
About the knife (knives). I've searched extensively on this. The consensus of both knowledgeable and ordinary people is that the knives were bought and then painted with the unusual dragon graphics by the movie prop department. As a semi-collector's item, I've considered buying one of the basic auto-stiletto, kriss blade type and getting an artist to mimic the dragon graphic. Unfortunately, the only pictures I can find or grab from the movie show the same side of both knives, so I have to assume both sides were painted the same. Here's a pic.
https://3.bp.blogspot.com/-PEGnvcSO2JU/UP8WBGGAEII/AAAAAAAAMw8/cv35OBhwklQ/s640/8.JPG