I have no idea.
(http://i390.photobucket.com/albums/oo343/snapmom/005-5.jpg)
That looks like a pipe vise jaws that you slip into a bench vise.
I'm with Ken - they do appear to be vise jaws of some sort.
I agree, though I have not seen them.
It may go on a splined shaft and a bolt tightens down for torque. bob w.
They look very much like pip holding inserts for a vise.
Ken W. is right, they are pipe jaws for a bench vise. Because of the rounded top to the cut out, they will fit a vise with an exposed screw. The cutout is to straddle the screw.
Would anyone like to have them?
Pipe Inserts for vise. Here is a pretty good picture.
http://www.ebay.com/itm/SUPERIOR-ERIE-TOOL-WORKS-ERIE-PA-USA-BENCH-VISE-43-1-2-REMOVABLE-PIPE-JAWS-/190719621604?pt=BI_Tool_Work_Holding&hash=item2c67c679e4
eBay no. 190719621604