Our mammal curators can identify a specimen from one of its hairs alone. But this kind of knowledge comes with years of experience.
The best way to identify anything is to compare it with others. This is why the collection here is the best tool a taxonomist has to identify an organism. Taxonomists use a combination of the collections and identification keys to identify organisms.
We identify different living things in different ways.
Not every specimen has full information with it. When researchers leave, the specimens they leave behind become vital references for interpreting their writings and concepts.