This is a good clean, antique, adjustable bit stock auger bit T-handle. It is 12 inch long overall, and has enough range capacity to handle most any of the medium to larger auger bits with the tapered square bit stock end. In the late 1800's these T-handles were usually designed for auger bits over 1" to 2.5" diameter as these would give the user plenty of leverage for that drilling application.  The auger bit can be held in place via an adjustable threaded steel insert in one handle, simply turn the handle clockwise to tighten the bit in place.  You should be able to use the old auger bits with the nut at the end of the taper also, provided you use a washer with that thread nut. The hardwood handles are nicely turned, very well made with steel centers and end caps.  Both are well attached, and firmly mounted, no cracks, good ferrules, solid, good threads, no rust. All in very good working order, not rust, clean. A good vintage tool, not marked but believed to be the same as a 1888 patented adjustable auger handle!