On a similar note: in "Prehistorik Road Trip", paleontologist Eileen Grogan remarks that shark fossils have a very characteristic smell. That's a human nose, talking about 323 million year old fossils.
Dogs being able to detect much more recent things does not surprise me at all
There are anecdotal reports of doctors/nurses able to pick up certain typical "illness smells" from their patients. Not sure if it's ever been studied more in depth.
Dogs can be trained to smell _cancer._ That is mind-bogglingly cool.