What is it? Set 391
 

2258: maybe for making a lead hammer? These are a common
item for machinery setup, and when they get out-of-shape, you just melt the
head down and cast a new one (around a steel-pipe handle). Usually
see these with left/right mold halves, though.
Or a mold for a Babbitt metal bearing, perhaps?

2261: decorative top for a shirt stud. The stud is small and fits
through the hole in the shirt, then you clip this top bit over it.