he'd seen it somewhere, damn it, somewhere...
Then he had it, from all those years ago. The girls' locker room, the hole in the wall, the broom closet. Sister Margaret. She'd had just this key hanging around her neck; he'd seen it clearly as she pinched his ear and got her own eyeful. For the few seconds she'd watched the two girls at play, she'd clutched this key inside a muscled fist, her lips moving soundlessly: this key, with the crossed hands forming the ring through which the simple loop of twine passed. There was no mistaking it.
As he looked at it now, he suddenly realized it wasn't a key after all. It had a tiny, was that a hinge along the shaft? He removed it from the box, dug with a fingernail at the little bolt or hinge or whatever it was. The "key" sprung open, revealing a narrow hollow chamber.
And rolled up inside the little tube was a tiny white cylinder of paper.