What is it? Set 511
 

2982 -- not a definitive answer, but the object on top looks like a gunsight that projects a semi-transparent reticle that appears to be located right on top of the target. I had one of the sights from a surplus store when I was a boy--I thought I remembered it was from a bazooka or something like that.

I'd guess it being a device for determining relative bearing of an object from a ship.

Northe