Since I've owned it: At least 30 years...
When I first got the machine, the film was missing that covered a light bank behind a one way mirror. When lit, the bonus shots are displayed to the player and appear to float over the playfield. Since the film had been missing, I had no idea what it looked like.
About 10 years ago, I read on RGP that a guy had purchased one, so I asked him to take some pictures. He did.
Today, with the aid of some backlight film, Gimp2 editor and an ink-jet printer, and those pictures, I made a new one.
Better late than never, I guess.
And yes, the game is still horrible, even when all the parts are there.