Anybody have an idea what this is? Thanks

Yes -- it is one piece of this ...

... but seriously ...
I believe this is a jeweling tool, for burnished jewel settings. The piece you have will open the lip of the old setting, using the tapered plunger to open the jaws wider or narrower. The other double-ended pieces have various sized cones and fit in the separate brass holder. They are used to burnish the setting down around the new jewel.