They are sighting periscopes for the M114, V100, and a myriad of other vehicles.
Basically they hard mount in the turret near the guns, fixed ahead in line with the direction the guns point. A mechanical arm from the gun cradle, via the linkage on the side of the scope, controls the head inside the periscope for elevation/depression so that wherever the viewfinder in the periscope looks, the guns are aimed (or vice versa).
It's a tad Rube Goldberg, but it works. Traverse, of course, is controlled by the turret itself moving. Hope that description makes sense.
Anyway, it is cheap, simple, and easy to maintain.
Attached is a picture of the V100 mount, hope that clarifies what I tried to explain above.
Not my V, by the way, but one I got to play in a while back.
Cheers
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