I guess that for this discussion's sake it would probably be better to leave the term kraton completely out of the conversation as it is bound to lead to confusion (i.e. the 'what constitutes a kraton keris' thread
) and merely refer to the term "quality" (which will, no doubt, also lead to confusion
). As i am sure you know Pangeran, tangguh is determined by an assessment of quite a number of aspects of the blade, including, but not limited to, the overall pawakan, type and quality of iron, type of pamor material, various ricikan and the manner in which they are executed, the weight of the blade, etc.
In a blade of "quality" these clues to the tangguh of the blade will fall within a very strict parameter. The better the blade, the easier, in theory, it should be to place it within it's appropriate tangguh. But as we descend downward in quality i would imagine this would become harder and harder to do. It would seem that the farther we move away from the strict standard of keris perfection, the less likely anyone would be capable of accurately placing it within a tangguh. Village pandai might find it harder to obtain the correct iron or quality of pamor material necessary to meet these standards. Lesser forging skills might create ricikan that don't quite fit neatly into the parameters of the day. Many keris might in fact display details from more than one tangguh. I do not believe that the tangguh system was developed to assess these types of keris.
As for circles that would refer to a newly made keris as a tangguh Mataram because it is made as a copy of a Mataram form, i suppose if you find enough people to agree with something you can call yourself a club, but i would personally have trouble with that assessment.
I am not familar with the term "yasan" and can't find it in any Indonesian dictionary. Is it a slang term?