Unbranded reloading die insert with 3/4 x 16 tpi threads on the insert body.  Vintage. Possibly Star or Phelps??? It looks like a swaging or priming die insert. Insert and  lock ring only.  Can't see any size markings. Rod measures  .200 at the tip and  . 215 up the shank. Overall length is 3 5/8" approximately.