Forgive the late reply, but I have been away from the site for a long time.
In the course of researching for the never-ending Thunderbolts, I think I have pretty well pinned down the story of this 4 inch shell. Allow me to share. Among Major Caleb Huse's many cannon purchases in England was a battery of at least four 4 inch steel Rifles made in early 1862 by Fawcett, Preston & Company. These guns were frequently misidentified by the Rebels as 18 pounder Blakely Rifles because the same Liverpool company made those better known guns - although none were of the 4 inch caliber. While all bore the "Fawcett, Preston & Co." maker's name, "Blakely Patent" was absent from these 4 inch guns. Evidently, this battery ran the blockade during late 1863 and arrived safely at the Richmond Arsenal. Classified as siege guns because of their size, on January 4, 1864, two of those misnamed "4 inch Blakely Rifle guns" accompanied by "two iron carriage for same" were sent to Gen. Maury in Alabama for the defense of Mobile. The remaining two were parked in the Arsenal's storage yard. One was sent to Fort Branch in North Carolina along with their limited supply of English-made ammunition. In 1972, it was lifted from the bottom of the Roanoke River and is shown in Beimeck's book. The one remaining gun was held as part of the artillery reserve and a supply of 4 inch projectiles ordered locally from A. J. Rahm who was then a primary source of 10, 20 and 30 pounder Read-Parrots for the Confederate Army. Rahm's January 1864 production record included 173 "4 in. Fawcett Shells," followed by an additional 115 in February. Many guns from the artillery reserve were rushed to the Peninsula when the Union made a surprise landing and advanced toward Richmond in August 1864. The Battle of Fussell's Mill followed and that's when examples of Rahm's 4 inch shells were fired into Malvern Hill. I have seen six or seven examples.
So, 24th Michigan (if you are still out there), you have a 4 inch smooth Read made by Rahm's Eagle Machine Works during Jan-Feb, 1864. All were well made with sturdy wrought iron sabots that do not appear to have been swedged or otherwise pre-rifled. All have an obvious circular mold seam half way up the ogive (slope of nose). Fuze holes on the couple I've seen without the fuze were bored off-center, like yours. The two I now show in Thunderbolts have the identical lathe dimple as yours. If that's not enough proof, I am told (by Jack M., I believe) that one is known with maker's initials "AR" stamped on the bearing surface. Your 4 inch Read is the only non-dug example I'm aware of. I love it!
Enclosed are pics of a 4 incher dug on the Peninsula.
Woodenhead