The word "pusaka" can have a number of separate, but related meanings, dependent upon the context in which it is used. It can be an heirloom, an inheritance, a ricefield that has been owned by one family for a number of generations, or it can be the physical object that links the current custodian of the pusaka to his forebears and to other living members of his kin group.
A pusaka need not necessarily be an item of wesi aji, such as keris, tombak, or pedang, but can be anything physical , such as a rice cooking pot, a saddle, or even a place of worship or of burial.
In Jawa prior to Kartasura, possession of the royal pusakas was held to be necessary to legitimise the right of the ruler to rule, however, disruption of the realm during the Kartasura era demonstrated that a ruler could indeed hold power in the absence of the royal pusakas. Even though this was shown to be the case, the royal pusakas can still be regarded as symbols of power.
Something I wrote several years ago gives a more in depth understanding of the the idea of "pusaka" as applied to the keris. This link will take you to this article:-
http://www.kerisattosanaji.com/KERISANDNAGA.html