I might have to get into the weeds abit here so that I can better understand the moving parts. Please excuse what might be pedantic.
The element of "respect" is still there, Empu Suparman used to say it was respect for the maker
Do you mean respect for the maker of the keris, by its current custodian or owner?
I suppose then this also means respect for all who have taken care of this keris ever since it was made, and the families and groups that it has bound together.
One thing is believed to be certain, and that is that an ordinary trade, dress or weapon keris made by an ordinary smith cannot have been made with spiritual content, simply because such a maker would not have known the mantras.
Yes that makes sense, and is a reminder that an empu is very different to a pandai keris, and that the empu was a person who through his works was able to create a conduit for the unseen in ways that are legitimate and potent to a Javanese person.
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The original question was "
in the Javanese belief system, what would make a keris worthy or eligible of being visited?" (emphasis added).
What if we were to remove that part of the question?
Could a keris have spiritual content or the potential for it, if it was to be made in a way that does not include all the Javanese belief system's particulars such as the right mantras?
I ask this question to Alan and others, but will attempt to elaborate and answer it myself to add to the discussion.
It makes sense that there are particularities that go into any artefact, product or outcome born from a belief system. Islam, for example, has many prayers and supplications for very specific things. Whatever it is that one needs to do in life, one can find in Islamic texts the right supplication to God. The specific utterances vary but invariably they are either praises to God or the Prophet, permission-seeking from God or protection-seeking from God.
No scholar of Islam would ever argue that your own words, with the right intent, directed to God would fall on deaf ears, but I guess the existence of specific prayers and supplications are a way of reaching God in a way that is deemed to be more refined. And refinement of the individual is probably the whole point of prescribed prayer and practices.
The point here is that mantras and prayers alike, specific ones as prescribed from a legitimate place in any belief system, matter.
But to who do they matter?
To continue with the Islam example, I would say that they mean less to God than they do to us. They are for humanity's sake, not for God's. But what about in the Javanese believe system where there are gods (including plenty enough room for the unitary, Abrahamic god), but ancestors, demons, animal spirits, nature spirits and so on? Do they need to hear those very specific words uttered with the right intents before they can do what they are called upon to do, like a password that only the initiated have? (I apologise in advance if that question comes off as crass. That isn't my intention).
There are many more questions and digressions I could add but it would all just be arriving at a final question, which is a metaphysical question within which the keris can be situated but stands on its own.
And that is:- how much of the unseen, and our relationship with it, can be accessed in a way that is unmediated by particulars, but in a way that is universal?
To bring that back to the keris:- suppose it is true that the ancestors can be honoured or worshipped, god can be honoured or worshipped, unseen beings can be offered to, by anyone in any way that is respectful, dignified and with sincere intent.
What does this mean for the keris when situated outside of its mother culture, belief system and practice? Can it still objectively (for lack of a better term) or truly be a spiritual object to the person with those beliefs who holds that keris? Or can a smith who is, say, an Aboriginal Australian shaman forge a keris and have it be a spiritual object?