I have the Uncharted promo ring..

[SwiftDeath]

Never seen it sell without the box

To be honest I think it would make a lot of buyers nervous

Because so many higher quality but unofficial nathan drake rings get sold on the various ebays that the box really adds credibility/authenticity to the sale

Personally I think it would be worth 100 - 125 USD max but my opinion of course

And again might have trouble selling it as most buyers have no means to verify the ring once they receive it as they don't have another copy to compare it with