It is, of course, pure speculation, but i wonder if these impliments didn't have some kind of talismanic purpose in the act of forging or just in general. Obviously they are of some special significance or the carvers of the Candi Sukuh stele and other reliefs in the area wouldn't have bothered to include them in the reliefs. Alan, do you recall the context in which the other examples appear, i.e., are they also being held? In similar fashion?
Some competent photographer need to take a trip to Jawa and do a careful and detailed photographic study of these carvings. I will be accepting travel funding in all forms beginning immediately.