Alam Shah, would think that is the effect someone attempted to copy, the gandik area was intentionally pitted, likely to hold some gold there also. Empu Kumis posted this link:
http://www.maritimeasia.ws/topic/iron.html , that seems to touch on "trade blades". Can anyone supply more on this, time periods, other swords? What was the demand for these keris if the customer is once or twice removed from the Empu, sort of deminishes the mystic aspect, & the keris does'nt seem to be the best weapon. Is there a "standard" or examples of what is typical about the trade blades. If only brittal Chinese iron was used would they not generally lack pamor & brake easily if used?