As there is a 
current discussion on a pattern-welded keris  I thought it might be worthwhile to reawaken this old thread of Lew's.
The darkened patches likened to veins of a leaf above are indeed iron inlays.
At first glance one thinks the blade is a single piece, but close examination does show there is a separate 
gangya with the seam from the angle largely hidden by one of the 
asang-asang. A number of additional images are included in the 
archive of Lew's collection.