Perhaps close-up pics of the edge would confirm the construction of the keris.
The base of the keris should be sandwiched, just that the softer outer layer completely envelopes the harder steel core. Not surprising, since the maker will have to fashion the greneng, kembang kacang, jalen, etc. Would make a whole lot sense to work on the softer material. Check out one of my keris pandai saras. The harder steel core only shows well above the base the blade.
http://www.kampungnet.com.sg/modules...view_photo.php