Hi nechesh. You will find the answer in the classification method. Java seems to have hierarchical classification, where though I'm not speaking to represent Bali view, I put forth classification which ovelaps each other. It means that keris could be BOTH pusaka and pertimi and as well as kadutan. The condition DOES co-exist and in fact strengthen one another as you said. Thus it is up to the owner to choose the way the keris speaks to him. It is in fact reflects how the owner respects the keris.
If it's always told to me that the keris is pusaka, ...I would have probably forget the esoteric properties, as I will be gazed at the history of it in the family. Thus, the calling is shifted, from the calling that represents owner subjective view, to calling that represents keris objective properties. Though it is still subjective, as I must say that the esoteric properties itself that makes it possible to color the history of the family.
In other possibility implication, to see a keris pertimi while it is not, is not something worth to discuss about.
I understand that people will want keris discussed in many perspectives possible including the age and origins of it, in antique/history perspective. I do agree with you though I personally think it will be very hard as keris is most kept and inherited as private belonging. The age is perhaps traceable, but to trace to first origin of the first owner or its family is almost impossible, unless you are somehow very close to a respected family which have the most secret treasured pusaka. Other way you will see only keris traffic, changing hands for how many, you would not imagine. If you really can sense the vibrating energy, you can be 50% sure the keris is old enough, and consider yourself lucky that the perishing energy is still there for you to find out, but that's if some prana master did not recently induce some of his magic to it. But if you can't sense it, I don't know which device is portable enough to carry to determine the age of the target.
~Ing ngarso sing tuladha, ing madya mbangun karsa, tut wuri handayani.