Since there is no method of holding a base plug against the bottom of the mould blocks, it might have been designed to cast against a flat surface. That will, of course, give poor casting due tothe temperature of whatever surface it is held against.

It does have that rebated rim I thought might be present, however since there isn't an elongated base, it doens't appear to have been made for a plug - although perhaps that is the way that one was made - ie: needs a plug to cast a hollow base.

The general shape of the bullet is so-minnie-like, which would be a mould originally for a cased rifle or double rifle - which would have been included with the round ball mould - according to Forsyth, in the mid 1800's for use n a muzzleloading rifle through into the 1890's for ctg. guns I'd think.

Intersting mould - cheap, and it's a project, for sure.

The diameter of the largest portions of the bullet are the important ones. The base band diameter and the diameter above the grease or crimping groove.