Trivia: Director Guy Hamilton called this the only Bond film he regretted making.
Trivia: Christopher Lee was said to hate the 'gadget' version of the Golden Gun (the one which could be assembled and taken apart on camera). The scene where Scaramanga kills Hai Fat had to be repeatedly re-shot because Lee kept having problems with getting the various pieces of his weapon to fit together properly.
Trivia: In the original novel, Scaramanga used a gold-plated Colt Single Action Army revolver, along with a gold-plated Derringer, as his weapons of choice. Both get a shout-out in the movie as Nick-Nack uses a Derringer on Bond at one point; then later, Scaramanga welcomes Bond to his island by shooting the cork out of a bottle of champagne with a Colt SAA revolver, referring to it as a 'harmless toy'.
Answer: I haven't been able to find any information on its whereabouts so my guess would be that ended up like most movie props do. Either as a souvenir for one of the people attached to the movie, (actor, director, etc.) in storage (in case it could be recycled as a prop in another movie) or simply discarded when it wasn't needed anymore.
Andreas[DK]