[Milsurplus] ? Odd cable ?

[Hue Miller]

Found this heavy coax cable jumper, about 6 ft. long. Each end has a 
threaded
collar; in fact, at first I thought it was a flex tuning cable, but the 
protrusion at
each end is not serrated or keyed or anything. The prong or center post is 
longer
and thinner than on a PL259 and the collar is too narrow and be able to 
screw
on. There is a metal tag collar at each end with the engraved legend,
RANGE MARK
no other markings.
So what is it?
And, it is available, free.
-Hue Miller