I'm pretty sure the circles are just for keeping the dangerous items in, not for keeping looters out. You can just reach in and grab it, if you're willing to risk the consequences. I'd present it to the PCs like that and see how they react.
If you include any amount of "do this, or roll this, to overcome" then game-ism will click in, and they'll just do it, and it will short-circuit the "should I?" process. Let it require nothing ... but just come with ominous and vague threats. More fun that way for a haunted crypt!
(Think of it like drawing from a Deck of Many Things. Sure, some items aren't bad ... but how many are you willing to pull?)
