Itachi Had in his possession at least two of the imperial regalia, being Totsuka's Sword and Yata's Mirror. So it would be to no ones suprise if he possessed the third The Yasakani Jewel. Therefore i beleive he gave Naruto the Jewel.
Sword-Valor
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Mirror-Wisdom
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Jewel-Benevolence
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I feel the Jewel has strong connection to The Sage of the Six Paths, first of all it looks like the necklace worn by him, secondly the necklace stands for benevolence meaning love and altruisity. Rikkoudo Sennin gave his younger son "The Body" for peace was needed to bring peace to the world.The younger brother's descendants later became known as the Senju, and the older brother's the Uchiha.
If you look closely at the Older Brother's eyes there are not the rinnegan but something else, something like a spiral. Naruto's mother is from the former Whirlpool Country, and Naruto's clothes are seen bearing a symbol. Therefore i beleive that the younger brother formed the whirpool under the name Uzumaki country, and their descendants the fire country under the name of Senju.
So i beleive Naruto to be of descent from the younger brother and has a very likely possibilty to unlocking a doujutsu and Itachi gave him the jewel to do so.