Hi Matahati, welcome to the forum! The blade of your keris has been made by twisting two bars of pamor tightly, these bars are then forged square and welded together, split apart again down the length as P. Abera notes and a piece of pamor inserted between the two, then re-welded. The pattern "fades" a little at the point due to forging-this has slightly "undone" the twist. Looking at it I can't see any steel core-makes life easier as you only have to make one set of twisted bars!!
