Karttikeya, I was taught a Solo interpretation of tangguh, by a Karaton empu who truly believed that if a keris was classified as tangguh Majapahit, it was made in the Kingdom of Majapahit, during the Majapahit era.
My teacher taught me as much as I was able to absorb between 1982 and 1995. I never, ever debated, nor argued about anything he taught me. When I was in his presence I accepted everything that he told me as indisputable fact, I adopted the Javanese mode of thought and I accepted all of the tenets of the Javanese keris belief system.
In discussion with a person who follows this belief system I still act in exactly the same way. I am not intent on changing the way in which people who follow Javanese keris beliefs and current philosophy see the keris and its place in the world. As far as I'm concerned everybody can believe whatever they wish. I don't argue with Muslims about their beliefs, I don't argue with Christians about their beliefs, and I don't argue with people who follow Javanese keris beliefs about their beliefs.
You tell us you are Indonesian, which might mean Javanese, or it might mean something else, but I am more than happy for you to believe whatever you wish about the truth of tangguh, and I will make no attempt to alter your beliefs.
If you care to go here:-
http://www.kerisattosanaji.com/keristangguh.html
you can read a short article I wrote some time ago in an attempt to assist people in western societies to understand a little of what "tangguh" means.
I am not asking you to accept this. You should continue to believe whatever you are happy to believe.
However, the fact remains, that much of the knowledge associated with keris is knowledge of a belief system, not knowledge of the keris. This can be demonstrated, but I am of the opinion that this forum is not the proper place to become involved in such a demonstration.
Although tangguh is a system that originated in Jawa, you will find that many Javanese people in Central Jawa hold a similar opinion about tangguh to my opinion. They express this by saying:-
Tangguh nggak sungguh ---I'm certain you will understand what this means.
Quite simply, tangguh is a classification system that was developed for a specific purpose, that purpose is now long past, and the system has become corrupted because of the tendency of many people to want to place a tangguh classification on every keris ever made, and if there is no classification that is suitable, they will invent one.
But I will not speak like this in Jawa.
As for "hasta brata" , I do not know the term. "hasta" is a measure that is given in cubits( units of about 46cm), "brata" I do not understand clearly, I think it is krama inggil, and is associated with the way in which one lives one's life and with meditation and holy attitude, or in another context, it can mean loyal or faithful I think --- as I said, I don't understand the word clearly. I do understand how blade angle is set, but that is a function of making a blade, not anything to do with classifying a blade.
Incidentally, there is nothing wrong with your English, it is clear and easy to understand. I know native speakers of English who write worse than you do.