Hello,
Just wanted to add to the discussion that from own experience I've seen some what I believe older pieces/have some age with similar pamor work coming from Madura, the blade shape as well. The other good example of pamor and other blade workmanship attributed to Madura (sometimes also East Java) is on photo 28A on Jean's book.
Can't say that the naga is later addition or not but I think it is a rare occasions for people adding a naga later. If the price of a keris with naga is a question, it might be cheaper to buy a complete keris with naga (say of the equal quality) then to commision a naga carving to a 'normal/standard'
gandik.
Hello Jean, welcome to the forum...
Thanks.