Only guessing for fun here. When Daryl noted the large diameter, it seemed like it was meant for one of the old .44 cartridges. A dip or tumble lube would likely be good as those seem to generally be low pressure and velocity.
It looks to be a purpose built mold, maybe from scrap, there wouldn't seem to be a reason for the threaded hole on the face of the female mold face. The sprue plate, handle components and bulk of the mold don't seem to have an antique origin.
Since I'm guessing on the mold, maybe, someone cobbled up a few brass tubing case walls grafted on to the head of a close donor cartridge. It's a short little bullet, likely for a revolver cartridge or similarly chambered carbine. There's not a whole lot of bore riding surface area for paper patching. Maybe.
It doesn't look like it was used much, which might be understandable. Still, it seems like part of some setup to get an old gun shooting. If there's no taper built in, she might have been a bullet sticker, but there aren't any signs of the outside being struck much to drop bullets. Interesting to see what folks might come up with.
