You're welcome, Richard.
Now that you show us the scabbard as well i think the keris is from Sumatra, Palembang. It certainly has some age. I strongly advise you use the cleaning Alan sugested.
Vinegar is a good option to soak it, but for more control i usually clean a blade with a slice of lemon or lime. That gives me more control on the cleaning process. But with te remains of gold on the gonjo i would be more careful as Alan said.
Sorry Alan for still using the term ganja in stead of gonjo. That's a dutch habbit just like we say Wrangka in stead of Wrongko. But i still do remember your wise lessons. But learning something new is easier than turning an old habbit into another one