It is the instrument that he played as the ship went down in the Atlantic, and that he later used as a buoyancy aid once Titanic went down.
The violin was discovered only by chance when the son of an amateur musician found it in his attic. It was given to his mother by her violin teacher and was left gathering dust.
The discovery was almost too good to be true, prompting experts to have the relic forensically examined by some of the most revered scientific bodies in Britain.
Now, after seven years of testing at a cost of tens of thousands of pounds, the water-stained violin has been proven to be the one played by Hartley on the night of the tragedy.
These pictures show how incredibly well-preserved the rose wood violin is despite its age and it being exposed to the sea for 10 days after the sinking.
There are two long cracks on its body that are said to have been opened up by moisture damage.
The photos also show the corroded engraved silver plate screwed onto the base of the fiddle that provided scientists with they key proof of its authenticity.
The historic violin, said to be worth a six figure sum, will go on public display at the Belfast City Hall, where Titanic was built, at the end of March.
Negotiations are also under way to exhibit it in museums around the world including America. It is likely to be auctioned off in the future.
Titanic experts have described it as the most important artefact associated with the infamous liner to have come to light.