Mystery tool

its a crimping tool

I believe it is could be used for crimping the copper collars you see on wire rope

and a very nice crimping from the looks of it.  Never seen one that old or one that you could flip over for more sizes to crimp.  

Don't know what it was for, but it sure would be handy for twisting wire handles for fuller tools, slitters. and hot cut chisles .

I second/third the crimper too. 4 sizes as pictured. Open it up, flip it around for more uses. As the outside has an uneven number of grooves, I'm thinking it could also be for holding 5 different sizes of cable for cutting and such.

one set of grooves is smooth and the other set has some textureing.

Pretty sure those are king crab leg crackers hehehe

I have a pair of those. they're old lineman

s crimpers.

Ben Smith is the closest to being on mark.  They were used by linemen to twist hard drawn copper overhead lines (making what was known in the 40s, and there about, as a Westinghouse splice).  You needed two sets of the "crimpers", as shown, with a proper space between them and then they were rotated about the axis of the wires that were placed in adjacent parallel grooves.  Some time during the 50s it became common to place the wires in a copper sleeve first and them twisting the bundle.