An item or thing can be duplicated perfectly, however it has to be covered in his blood. If it's something that has extraordinary traits those traits often cannot be transferred over unless it soaks in his 'living' blood* for, like, a Long Time.
* - specifically blood cycled by his heart so no like 'putting it in blood donation packs'
ex: Can copy his own liver perfectly.
ex 2: a coin that has weak magical powers has to be sewed up under his skin for 2 years or something before it can be copied and have similar magical powers.