Came across this the other day. Any ideas? The machining on the pointed end is threads- not parallel circles.
Ignore the note under the pics,I can,t seem to be able  to delete it.

Left-hand threaded? Maybe a screw/pipe extractor?

That could be a possibility, I found this at my place at the lake which I will not be back to for a few more days. I am about 95% sure that the threads are right handed but I will check and let you know.

I don't know their proper name, but the pictures look very much like the plugs my father in law carried with him when he worked as a pumper for wells in the Oklahoma oil field. They were use to patch holes in oil storage tanks, sometimes a rusted out hole, sometimes a bullet hole. He would just screw them in until they stopped the leak. As far as I can remember, that was considered a "permanent" repair.

Hope this helps!

Bill D.

http://www.usaindustries.com/THREADED_TAPERED_PLUGS.php

Bingo...

That is definitely what it is.Thanks guys.