Brian, I'm out of my depth here!
The gun, as you pointed out, is NOT a Bofors but two Browning aircraft machine guns on some sort of anti-aircraft mounting, probably for airfield defence. I would suspect that the guns are mounted staggered to allow the ammunition belts not to interfere with each other.
The sight is obviously common to both guns, and mounted between them.
The projector is similar, but naturally less modern. The 1962 one was fitted on a cabinet with wheels, much like a mechanic's tool chest. The one in the picture is projecting the image on to a mirror, and this would then be turned and tilted to make the image on the dome move. Thus speed could be altered, as well as the angle of flight. I would imagine that this was limited to half the dome, 90 degrees to the left and to the right of the projector, but this should not have been a problem since each anti-aircraft gun would usually have a limited arc of fire in action.
Hope this helps.
Godwin
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George Cross Island
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