Of course tangguh is not a measurable concept : it was never intended to be.
It is an opinion.
If you get a number of people with a similar high level of experience you will get minimal variation in opinion on tangguh. Old will never, ever be confused with recent. Surakarta will never be confused with Mataram.
If you get a number of half-baked nitwits providing opinions, especially half-baked nitwits trying to sell keris, you'll get Koripan presented as Mataram Sultan Agung and God alone knows what other stupidity.
The problem is that for many years tangguh has been used incorrectly, by both dealers and collectors, and it has completely moved away from what it was originally intended to provide:- a system that would permit the estimate of an approximate value for an investment property.
It was never intended to be applied to run-of-the-mill keris churned out as a common man's weapon or dress item.
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