It is not a Confederate artillery fuze... but it is a very "special" part from one. Your find is the brass support-plug from underneath a Confederate-made Bormann fuze. Here's what is "special" about yours:
In 1861, the Confederates began manufacturing their own version of the US-made Bormann timefuze for artillery shells. But they were never able to match yankee industry's production-quality. The Confederate version of the Bormann timefuze frequently malfunctioned, either failing to ignite, or burning for too short or too long of time, or detonating instantly when the shell was fired (sometimes exploding the shell before it had time to leave the cannon's barrel). So, at the start of 1863, the Confederate Army Ordnance Department discontinued manufacture of their version of Bormann fuze. Existing supplies of that fuze did eventually get used up, by "converting" some of the CS-made Bormann fuzes to use the old simple paper-bodied timefuze. The conversion was accomplished by drilling a tapered 1/2"-to-7/16" hole down through the center of the Bormann fuze AND the brass support-plug underneath the fuze. Because the support-plug screwed into the shell's fuzehole, trying to drill through the support-plug in the shell would cause it to spin, which "unscrewed" it downward into the shell's powder-cavity. So, to lock the support-plug into the fuzehole before drilling, several small holes were PARTLY drilled into the support-plug, around the edge of its flat top. Your find is one of those very rare "converted" Confederate Bormann timefuze support-plugs (from an exploded shell). See photos and info on page 27 of the book "Artillery Fuses Of The Civil War" by Charles H. Jones. He calls it a "drilled CS Bormann fuze underplug." He reports that the conversion was done only at the Selma Alabama and Augusta Georgia CS Arsenals. Congratulations on your VERY scarce find.
After I posted my reply, the thought came to me that I should have included some photos to illustrate what I was talking about.
The Bormann timefuze's support-plug (which some people call the underplug) screwed into the support-shelf, which is a circular projection at the bottom of the "main" fuzehole. See the first photo.
The second photo shows a sawed-in-half Confederate Bormann-fuzed roundshell. In it, you can see the brass support-plug in position directly underneath the Bormann timefuze.
I am amazed almost daily of the knowledge that Pete (TheCannonBall Guy) has. I have dug and fooled with civil war relics for about 43 years now and I am constantly learning things from Pete. He knows military relics from almost every era and for those of you who don't know, he along with Tom Dickey, literally wrote the book on civil war artillery. We all owe him a great deal for his time and knowledge.
This is why I like metal detecting so much... You never what your going to learn from your dug up treasures next... Awesome find and excellent explanation of what it was...