What...you don't shoot a .50 cal? Missed the Beck info and couldn't see anything other than the thumbnails at the time. Beck makes core drills, reamers and countersinking tools. Their online info does mention deburr tools, but does not show any. An educated guess from looking at the pictures, it's a production tool that has been modified at home for a particular task. The tips of the cutting leaves have been ground off and they do not look even or flat in the photo, so probably done freehand. The stepped pilot shows being turned in a lathe, but not by someone that is normally a machinist. The surface finish of the cut area and the stepped nub at the end screams home shop with very little turning experience.
You should be able to get a few buck on it at least.