Well technically Madura is administered as "East Jawa", so calling this an East Jawa keris does not seem incorrect to me. Certainly we do see keris that seem more likely to have come specifically from the island of Madura, but this keris looks like it could go either way.
I see what Gio was hoping might be engraving marks on the blade for kinatah attachment, but i think Gustav is probably correct that this is just bade erosion. I have certainly seen worse condition on blades, but would fall short on calling this one "in good condition". However Athanese, i believe it would indeed be in your best interest (and that of this keris) to continue your cleaning process to remove all the rust on this blade. A good long soak in a mild acidic bath such as pineapple juice with frequent brushing with a toothbrush should clean it up nicely without causing any further damage to the blade. Then neutralize the acid with a slurry made with baking powder. This should not only not damage your blade, but will prevent further erosion that the remaining rust will cause over time.
