I think it has to be a version of Archer's patented percussion fuse. Two similar examples are pictured below. The first is in a rifled 12 pounder Mullane dug at Vicksburg, I think. The second is in a smaller 3 inch Read dug at Gettysburg. Maybe the head of your fuse was crushed flat when it hit something perpendicular or maybe it was among the experimental ordnance fired into the banks of the James River east of Richmond. The basic form was cast prior to turning it down which explains why it is so thick at the bottom. If threads are absent, the South sometimes put lead plugs in the bottom of their fuses. Later, the Rebs figured a way to make thinner Archer fuses out of sheet brass. I believe the bottom of this one was threaded for a plug which blew out when the projectile exploded. The CS Army's ordnance authorities rejected the Archer fuse because it worked poorly unless it hit perpendicularly. In the field, very few impacted head-on. The slider tended to get stuck in the fuse body and malfunction. They rejected Girardey's excellent percussion fuse for the same reason. The CS Army slowly developed the deeply flawed Broun concussion fuse instead based on the popular Britten concussion fuse. By contrast, the CS Navy loved Archer's invention and ordered many for their large and small caliber shells until the end of the war.
So, here is my theory. If your fuse did not come from a testing range, then it was probably fired by a small CS gunboat ( they had many) from a 3 inch Rifle or 10 pdr. Parrott during one of the many actions that occurred on that section of the James River. Likely from a CS Navy projectile.
Best, Woodenhead
