The Thomas-&-Thomas "Handbook Of Civil War Bullets & Cartridges" shows it as bullet #170, saying "Southern manufacture, nose cast, cone cavity."
I've seen some that were dug in early-to-midwar Virginia sites. Due to it being roundish-nosed and having a snipped-off nosecasting sprue, with three non-standard grooves, before it showed up in the T&T book local Virginia diggers/collectors called it a Confederate imitation of the so-called "US Harper's Ferry Pistol-Carbine minie" (which is now known as the US Willaims Regulation minie). Because of the Virginia finds, and the one listed at Bullet & Shell as being dug in Lowcountry SC, I can't say whether it was made in VA or SC. Seems like if it was made in SC, quantities of them would've been found in the Charleston siege lines and camps.
Regards,
Pete