IT APPEARS TO BE EITHER A LAYER OF VERY OLD STABELIZED RUST EXCEPT WHERE THE BLADE EDGES WERE SHARPENED OR A BLACK FORGED FINISH THAT IS INTACT AND RUSTED OVER EXCEPT FOR THE SHARPENED AREAS. NO DOUBT THE ITEM WAS CARRIED BY THE ORIGINAL OWNER AND COLLECTED THAT WAY LONG AGO.
IF YOU KNOW SOMEONE WHO FORGES BLADES LET THEM TAKE A LOOK AND GET THEIR OPINION. THE BLACK FORGED FINISH IS COMMON IN AFRICA BUT I HAVEN'T SEEN IT FROM SUMATRA. THIS LOOK AND FINISH SETS THIS COJANG APART FROM ALL OTHERS I HAVE SEEN SO I WOULD CONSIDER THAT BEFORE CLEANING IT UP TO LOOK LIKE ALL THE OTHERS. IF ACTIVE RUST IS PRESENT STABELIZE IT REGARDLESS OF YOUR DECISION AND YOU COULD PICK SOME OF THE BLACK OFF THE DESIGNS TO MAKE THEM CLEARER WITHOUT CHANGEING IT MUCH. A INTERESTING SWORD.
