To assess/judge quality of something, we must understand how those things were made, the material and process used, and what the really purpose of those things. This also apply to keris. Contrary to common belief, judging a pusaka keris, firstly, is a very rational process. After that, you should use your own "feeling". No dukuns and incenses involved
First of all, about the making process and materials used.
One of the important processes in keris making is "mewasuh besi". wasuh=basuh=cuci=to wash/clean. This is the first step in forging pusaka. We all know, the ancient iron produced by smelting, and had a lot of impurities inside. The empu drove off the impurities by layering the iron (heating the bar, elongated it, fold it back, welding it, repeating the process for many times). Remember though, this process done before the iron mixed with the pamor. Basically, the empu was making a very pure iron. It takes a lot of effort and a good materials, and seem to be skipped if the empu just made an ageman keris. Empu Djeno said, it takes 12-14kg iron just to make a single keris, not to mentions the steel and pamor materials, if he followed the process used by Empu Pangeran Sedayu / Supo Mandrangi, the famous empu of Majapahit. The characteristics of clean iron, amongs others, are: withstand the high/welding temperature and giving little sparks in this bright-yellow temperature, resilient, and withstand the corrosion. Having the pure iron is very important, not only technically (that is, giving resilient and corrosion-resistant characteristics to the blade, as a weapon) but also esoterically (empu Jeno said, his prayer would be more easily "answered" and "get into" the blade if he works on this iron), and philosophically (which we may discuss later). On the finished blades, there are 3 classes/categories of this "clean" irons : Nyabak = look like sabak=batu tulis=slate, that is, smooth, clean and dense iron. This would be the minimal iron's quality for pusaka keris; Nyerat=serat=fibrous iron, better quality blades ; gulali = look like gula-gula/candy/melting sugar, the best quality iron/blades. Identifying this "clean iron" would be the most important point in assessing pusaka. Just remember then, the assessor must be able to discriminate the smooth-clean characteristic caused by polishing or by the iron itself.
After passing the "Iron exam", then we should examining how the pamor integrated to the iron. I believe, in better quality keris, the pamor material would also be "washed", just like the iron. The earthly iron symbolize the human, in this case, the owner of keris. Pamor then symbolize the heavenly fate, no matter where it came from (celestial or terrestial). Before "catching" and "unite" with the heavenly fate, the human-being should be "clean" spiritually. That why the "clean iron" is important philosophically. Pamor, in other case, should be integrated "properly" to the iron, according to the empu's intention. Many times, the empu fail to do it properly, just like Monet painting his water lotus series. While he painted over 200 paintings, only a few of them, he himself thought, as "properly" showing his intention.
Other exam would be the "garap", that is, how the ricikan (details) were made, and "guwaya", the overall looking of the keris. This exam involve your "feeling". Pusaka keris should have "personality". Haryono Guritno classified keris in 10 grades. the best would be "mahanani", came from "ana"=being, that is, a keris which is when unsheathed, the "aura" or "character" would be easily felt by any attendants in the room. Just like a good painting changing the "aura" of the room. Once again, need no dukun or incense here. Just your feeling.
Wish may help. Handling a pusaka by ourselves might means thousands words
Good hunting !